Annotate/Document User-Defined Functions

[Denneisk]

Allow descriptions and potentially further annotations (nodiscard, ...?) for UDFs. This would be mostly useless currently, but it'll be a useful framework for the future with a better editor/E2Helper.

## This function does something really cool!
function myFunction() {} # Looking up "myFunction" with intellisense will show the above comment as its description.

Using ## or ///.

Would also be cool if (global) variables could have descriptions.

/// Stores the number of kills
Kills = 0

This, (along with a hopefully new E2Helper that includes UDFs), would be very useful for library developers.