Detect when phase 3+ WASM proposals get merged into main spec

Same as #307 but for WASM proposals.

See [Finished proposals](https://github.com/WebAssembly/proposals/blob/main/finished-proposals.md) for the list of WASM proposals that got merged into the main spec and [Inactive proposals](https://github.com/WebAssembly/proposals/blob/main/inactive-proposals.md) for the list of WASM proposals that were discontinued.