feat: generic type arguments

[Jan0660]

For ExternThings: #System.Collections.Generic.List<#int> (-> GenericExternThing?)
For Methods: #System.Linq.Enumerable:Select<#int, #float>(...) (-> GenericKeyword?)

Theoretically also allowing the type names inside the generic type specification to be specified without the # should be possible and would look nicer I guess.