Add warning about deprecation

[athei]

Parity will no longer maintain this. We will be pushing for making wasmparser and wasmencoder no_std compatible.

[hunjixin]

@athei could you show me the code about wasmparser/wasmencoder for reference

[hunjixin]

https://github.com/bytecodealliance/wasm-tools/tree/main/crates/wasm-mutate/src

[athei]

If you only want to parse (but not write) and need no_std you should use this: https://crates.io/crates/wasmparser-nost

[hunjixin]

If you only want to parse (but not write) and need no_std you should use this: https://crates.io/crates/wasmparser-nost

edit wasm is not easy to use

[HCastano]

🪦