[ENHANCEMENT] Add extensions and optional fields parsing for typedefs.

[Starexify]

This PR adds correct parsing for optional and extensions in typedefs.

For example this snippet:

typedef TestTypedef = {
	var id:Int;
	var data:T;
	var ?version:Float;
}

typedef ExtendedTypedef = {
	> TestTypedef,
	var description:String;
}

The hscript parser would complain (images below) about the unexpected > and ? symbols before, but now it parses correctly the extensions and optional fields like version.