Typeclass Prototype Syntax Hightlighting w/ Parentheses

There is an open issue with the XCSL syntax highlighter, specifically within parameterized prototypes.

For a practical example, see the following code:
`parse_ast string (token list) = ast`

In the above code, the following elements are colored correctly:

- parse_ast
- token list
- ast

No file or test is named. Reproduce the XCSL example `parse_ast string (token list) = ast` in the extension, then trace the syntax-highlighting rules for parameterized prototypes. Done means the parentheses and their contents receive the intended highlighting while parse_ast, token list, and ast remain correctly colored.

Scritto dal modello di indicizzazione a partire dal testo della issue.