docs: update ipld/multiformats docs (#3771)

Improve docs around how to configure custom block codecs/multibase
codecs, etc.

docs/IPLD.md

@@ -3,29 +3,46 @@
 ## Table of Contents <!-- omit in toc -->
 
 - [Overview](#overview)
-- [Bundled Codecs](#bundled-codecs)
-- [Adding additional codecs](#adding-additional-codecs)
+- [Bundled BlockCodecs](#bundled-blockcodecs)
+- [Bundled Multihashes](#bundled-multihashes)
+- [Bundled Multibases](#bundled-multibases)
+- [Adding additional BlockCodecs, Multihashes and Multibases](#adding-additional-blockcodecs-multihashes-and-multibases)
 - [Next steps](#next-steps)
 
 ## Overview
 
-The IPFS repo contains a blockstore that holds [Blocks](https://github.com/ipld/js-ipld-block). These blocks can be thought of as a [CID][] and associated byte array.
+The IPFS repo contains a blockstore that holds the data that makes up the files on the IPFS network. These blocks can be thought of as a [CID][] and associated byte array.
 
-The [CID][] contains a `codec` property that lets us know how to interpret the byte array associated with it.
+The [CID][] contains a `code` property that lets us know how to interpret the byte array associated with it.
 
-In order to perform that interpretation, an [IPLD Format][] must be loaded that corresponds to the `codec` property of the [CID][].
+In order to perform that interpretation, a [BlockCodec][] must be loaded that corresponds to the `code` property of the [CID][].
 
-## Bundled Codecs
+Similarly implementations of [Multihash][]es or [Multibase][]s must be available to be used.
 
-js-IPFS ships with three bundled codecs, the ones that are required to create and interpret [UnixFS][] structures.
+## Bundled BlockCodecs
+
+js-IPFS ships with four bundled codecs, the ones that are required to create and interpret [UnixFS][] structures.
 
 These are:
 
-1. [ipld-dag-pb](https://github.com/ipld/js-ipld-dag-pb) - used for file and directory structures
-2. [ipld-raw](https://github.com/ipld/js-ipld-raw) - used for file data where imported with `raw-leaves=true`
-3. [ipld-dag-cbor](https://github.com/ipld/js-ipld-dag-cbor) - used for general storage of JavaScript Objects
+1. [@ipld/dag-pb](https://github.com/ipld/js-dag-pb) - used for file and directory structures
+2. [raw](https://github.com/multiformats/js-multiformats/blob/master/src/codecs/raw.js) - used for file data where imported with `--raw-leaves=true`
+3. [@ipld/dag-cbor](https://github.com/ipld/js-dag-cbor) - used for storage of JavaScript Objects with [CID] links to other blocks
+4. [json](https://github.com/multiformats/js-multiformats/blob/master/src/codecs/json.js) - used for storage of plain JavaScript Objects
+
+## Bundled Multihashes
+
+js-IPFS ships with all multihashes [exported by js-multiformats](https://github.com/multiformats/js-multiformats/tree/master/src/hashes), including `sha2-256` and others.
+
+Additional hashers can be configured using the `hashers` config property.
+
+## Bundled Multibases
+
+js-IPFS ships with all multibases [exported by js-multiformats](https://github.com/multiformats/js-multiformats/tree/master/src/bases), including `base58btc`, `base32` and others.
 
-## Adding additional codecs
+Additional bases can be configured using the `bases` config property.
+
+## Adding additional BlockCodecs, Multihashes and Multibases
 
 If your application requires support for extra codecs, you can configure them as follows:
 
@@ -35,14 +52,34 @@ If your application requires support for extra codecs, you can configure them as
 
     const node = await ipfs({
       ipld: {
-        // either specify them as part of the `formats` list
-        formats: [
-          require('my-format')
+        // either specify BlockCodecs as part of the `codecs` list
+        codecs: [
+          require('custom-blockcodec')
         ],
 
-        // or supply a function to load them dynamically
-        loadFormat: async (format) => {
-          return require(format)
+        // and/or supply a function to load them dynamically
+        loadCodec: async (codecNameOrCode) => {
+          return require(codecNameOrCode)
+        },
+
+        // either specify Multibase codecs as part of the `bases` list
+        bases: [
+          require('custom-multibase')
+        ],
+
+        // and/or supply a function to load them dynamically
+        loadBase: async (baseNameOrCode) => {
+          return require(baseNameOrCode)
+        },
+
+        // either specify Multihash hashers as part of the `hashers` list
+        hashers: [
+          require('custom-multibase')
+        ],
+
+        // and/or supply a function to load them dynamically
+        loadHasher: async (hashNameOrCode) => {
+          return require(hashNameOrCode)
         }
       }
     })
@@ -53,14 +90,34 @@ If your application requires support for extra codecs, you can configure them as
     const client = ipfsHttpClient({
       url: 'http://127.0.0.1:5002',
       ipld: {
-        // either specify them as part of the `formats` list
-        formats: [
-          require('my-format')
+        // either specify BlockCodecs as part of the `codecs` list
+        codecs: [
+          require('custom-blockcodec')
+        ],
+
+        // and/or supply a function to load them dynamically
+        loadCodec: async (codecNameOrCode) => {
+          return require(codecNameOrCode)
+        },
+
+        // either specify Multibase codecs as part of the `bases` list
+        bases: [
+          require('custom-multibase')
         ],
 
-        // or supply a function to load them dynamically
-        loadFormat: async (format) => {
-          return require(format)
+        // and/or supply a function to load them dynamically
+        loadBase: async (baseNameOrCode) => {
+          return require(baseNameOrCode)
+        },
+
+        // either specify Multihash hashers as part of the `hashers` list
+        hashers: [
+          require('custom-multibase')
+        ],
+
+        // and/or supply a function to load them dynamically
+        loadHasher: async (hashNameOrCode) => {
+          return require(hashNameOrCode)
         }
       }
     })
@@ -69,7 +126,11 @@ If your application requires support for extra codecs, you can configure them as
 ## Next steps
 
 * See [examples/custom-ipld-formats](https://github.com/ipfs/js-ipfs/tree/master/examples/custom-ipld-formats) for runnable code that demonstrates the above with in-process IPFS nodes, IPFS run as a daemon and also the http client
+* Also [examples/traverse-ipld-graphs](https://github.com/ipfs/js-ipfs/tree/master/examples/traverse-ipld-graphs) which uses the [ipld-format-to-blockcodec](https://www.npmjs.com/package/ipld-format-to-blockcodec) module to use older [IPLD format][]s that have not been ported over to the new [BlockCodec][] interface, as well as additional [Multihash Hashers](https://www.npmjs.com/package/multiformats#multihash-hashers).
 
-[cid]: https://www.npmjs.com/package/cids
-[ipld format]: https://github.com/ipld/interface-ipld-format
+[cid]: https://docs.ipfs.io/concepts/content-addressing/
+[blockcodec]: https://www.npmjs.com/package/multiformats#multicodec-encoders--decoders--codecs
 [unixfs]: https://github.com/ipfs/specs/blob/master/UNIXFS.md
+[ipld format]: https://github.com/ipld/interface-ipld-format
+[multihash]: https://github.com/multiformats/multihash
+[multibase]: https://github.com/multiformats/multibase