Merge #817

817: Add feature matrix document r=MarkMcCaskey a=MarkMcCaskey

[rendered](https://github.com/wasmerio/wasmer/blob/docs/add-feature-matrix/docs/feature_matrix.md)

# Review

- [x] Create a short description of the the change in the CHANGELOG.md file


Co-authored-by: Mark McCaskey <mark@wasmer.io>
Co-authored-by: Mark McCaskey <markmccaskey@users.noreply.github.com>

CHANGELOG.md

@@ -6,6 +6,7 @@ Blocks of changes will separated by version increments.
 
 ## **[Unreleased]**
 
+- [#817](https://github.com/wasmerio/wasmer/pull/817) Add document for tracking features across backends and language integrations, [docs/feature_matrix.md]
 - [#823](https://github.com/wasmerio/wasmer/issues/823) Improved Emscripten / WASI integration
 - [#821](https://github.com/wasmerio/wasmer/issues/821) Remove patch version on most deps Cargo manifests.  This gives Wasmer library users more control over which versions of the deps they use.
 - [#820](https://github.com/wasmerio/wasmer/issues/820) Remove null-pointer checks in `WasmPtr` from runtime-core, re-add them in Emscripten

docs/feature_matrix.md

@@ -0,0 +1,26 @@
+# Feature Table
+
+## Compiler Backend
+
+|   | Singlepass | Cranelift | LLVM |
+| - | - | - | - |
+| Caching | ❌ | ✅ | ✅ |
+| Emscripten | ✅ | ✅ | ✅ |
+| Metering | ✅ | ❌ | ✅ |
+| Multi-value return | ❌ | ❌ | ❌ |
+| OSR | 🚧 | ❓ | ❓ |
+| SIMD | ❌ | ❌ | ✅ |
+| WASI | ✅ | ✅ | ✅ |
+
+
+## Language integration
+
+TODO: define a set of features that are relevant and mark them here
+
+Current ideas:
+
+- WASI FS API
+- Callbacks
+- Exiting early in hostcall
+- Metering
+- Caching