Add support for function attributes

[GGG-KILLER]

What lua version(s) is this feature from?

Luau

What feature are you requesting?

Attributes allow extra metadata to be added to functions.

Can you go in further detail of what this feature is about?

https://luau.org/grammar
https://rfcs.luau.org/syntax-attributes-functions.html

Please ensure you have done the following actions:

• I have checked that there are no similar requests already open.
• I have confirmed that this has not been implemented on the latest nightly version.
• I have confirmed that this is a custom syntax that requires modifications to be supported.
• I acknowledge my issue will be closed if any step has been skipped.