Implement Directives grammar

[Directives | TypeSpec](https://typespec.io/docs/language-basics/directives/) It seems that `#deprecated` and `#suppress` are documented for now. Now it seems that the parser is partially broken if `#` is included. The semantic one should be handled by LSP, so we should just deal with it in a messy and sharp way. I will try to see if I can implement it.