Describe workflow for testing preview2 components (#7292)

* Describe workflow for testing preview2 components

* format text

docs/contributing-implementing-wasm-proposals.md

@@ -124,3 +124,31 @@ default in Wasmtime, and can be used as a review checklist.
 
 [phases]: https://github.com/WebAssembly/meetings/blob/master/process/phases.md
 [WABT]: https://github.com/WebAssembly/wabt/
+
+## Adding component functionality to WASI
+The [cap-std](https://github.com/bytecodealliance/cap-std) repository contains
+crates which implement the capability-based version of the Rust standard library
+and extensions to that functionality. Once the functionality has been added to
+the relevant crates of that repository, they can be added into wasmtime by
+including them in the preview2 directory of the [wasi crate](https://github.com/bytecodealliance/wasmtime/tree/main/crates/wasi). 
+
+Currently, WebAssembly modules which rely on preview2 ABI cannot be directly
+executed by the wasmtime command. The following steps allow for testing such
+changes.
+
+1. Build wasmtime with the changes `cargo build --release`
+
+2. Create a simple Webassembly module to test the new component functionality by
+compiling your test code to the `wasm32-wasi` build target.
+
+3. Build the [wasi-preview1-component-adapter](https://github.com/bytecodealliance/wasmtime/tree/main/crates/wasi-preview1-component-adapter)
+as a command adapter. `cargo build -p wasi-preview1-component-adapter --target
+wasm32-wasi --release --features command --no-default-features`
+
+4. Use [wasm-tools](https://github.com/bytecodealliance/wasm-tools) to convert
+the test module to a component. `wasm-tools component new --adapt
+wasi_snapshot_preview1=wasi_snapshot_preview1.command.wasm -o component.wasm
+path/to/test/module`
+
+5. Run the test component created in the previous step with the locally built
+wasmtime. `wasmtime -W component-model=y -S preview2=y component.wasm`