Include parents in function, decorator bodies

I customized the [highlights.scm](https://github.com/heaths/helix/blob/main/runtime/queries/typespec/highlights.scm) for my [Helix](https://github.com/helix-editor/helix) language support for TypeSpec and noticed that functions' and decorators' bodies are inconsistent with operations' body when it comes to including `()`. Compared to other language support in Helix, a gesture like `mif` (select inside function) or `mit` (select inside type) includes the parents/brackets but this does not seem achievable with functions and decorators because the parens are not part of the parameter list token. I'm happy to submit a PR if you're open to having them included like they are for operations' body / param list. [](https://asciinema.org/a/VkGbOYkrgohBboBVDTnGQkiLB)