docs: Update README

[mhmd-azeez]

• Write a similar README to go-pdk https://github.com/extism/go-pdk
• Change the API to make it more convenient
  • Move allocate, allocateBytes, findMemory to Plugin. Since Memory is not public, there was no way to call them
  • Added setError and setErrorMemory
  • Added getVarInt and setVarInt
• fix build errors

Fixes #16

[mhmd-azeez]

Not sure why there were some build errors on my machine

[nilslice]

@mhmd-azeez - thank you! which version of Zig are you using with this?

I'm on 0.12.0-dev.978+78855bd21, and seem to need to use std.builtin.Endian.Little (vs. std.builtin.Endian.little, note the capitalization of little). I am not sure if this is a version thing or a typo haha

[mhmd-azeez]

@nilslice seems like they have changed it to little in the newer versions:

PS D:\dylibso\zig-pdk> zig build
zig build-exe Basic example Debug wasm32-freestanding-musl: error: the following command failed with 2 compilation errors:
D:\tools\zig.exe build-exe D:\dylibso\zig-pdk\examples\basic.zig --cache-dir D:\dylibso\zig-pdk\zig-cache --global-cache-dir C:\Users\muham\AppData\Local\zig --name Basic example -rdynamic -target wasm32-freestanding-musl -mcpu generic --mod extism-pdk::D:\dylibso\zig-pdk\src\main.zig --deps extism-pdk --listen=-
Build Summary: 0/3 steps succeeded; 1 failed (disable with --summary none)
install transitive failure
└─ install Basic example transitive failure
   └─ zig build-exe Basic example Debug wasm32-freestanding-musl 2 errors
src\main.zig:31:73: error: enum 'builtin.Endian' has no member named 'Little'
            std.mem.writeInt(u64, buf[i..][0..8], x, std.builtin.Endian.Little);
                                                                        ^~~~~~
D:\tools\lib\std\builtin.zig:452:20: note: enum declared here
pub const Endian = enum {
                   ^~~~
referenced by:
    count_vowels: examples\basic.zig:19:25
    remaining reference traces hidden; use '-freference-trace' to see all reference traces
src\Memory.zig:42:78: error: enum 'builtin.Endian' has no member named 'Little'
        const data = std.mem.readInt(u64, buf[i..][0..8], std.builtin.Endian.Little);
                                                                             ^~~~~~
D:\tools\lib\std\builtin.zig:452:20: note: enum declared here
pub const Endian = enum {
                   ^~~~
PS D:\dylibso\zig-pdk> zig version
0.12.0-dev.1664+8ca4a5240

[mhmd-azeez]

Hah! it's been changed 3 weeks ago: ziglang/zig@3fc6fc6

[nilslice]

haha! thank you for looking at that. sorry I was behind a few versions... I think our strategy has been to follow the latest versions as close as possible.

@usdogu can advise, as the expert Zig extism contributor!

[mhmd-azeez]

In addition to reviewing the API changes, please also take a close look at the examples to make sure allocations and deallocations are properly managed

[bhelx]

Thanks for taking this one on!

[usdogu]

Other than these, LGTM!

[mhmd-azeez]

@usdogu thank you very much for you suggestions!

[mhmd-azeez]

Also added the readme examples to basic.zig, we can turn them into integration tests

[nilslice]

Going to merge this one & make sure #19 works based on it