Syntax highlighting and outline support for empirical `fun` definitions

[joeldrapper]

I realise this is a very unusual use of Ruby so completely understand if you’d rather not merge it here. I’ve written TreeSitter queries to support fun definitions from Empirical with syntax highlighting and outline support.

https://github.com/yippee-fun/empirical

These queries are so specific, it’s extremely unlikely that they would be triggered for anyone who isn’t using Empirical. You would need to have a call pattern like this in your code.

fun foo => void do
end