feature: support chatette files

[ObserverOfTime]

Did you check the tree-sitter docs?

• I have read all the tree-sitter docs if it relates to using the parser

Is your feature request related to a problem? Please describe.

Chatito & chatl files are supported but chatette files are not.

Describe the solution you'd like

Add support for chatette files and highlight tests.

Describe alternatives you've considered

N/A

Additional context

I've never used chatette and the spec is significantly more complicated than chatito & chatl.
If anyone is interested in implementing it, there's some preliminary work in the chatette branch.