RFC: Unique syntax for metatable types

[ffrostfall]

Rendered

[Wunder-Wulfe]

I believe this would be very helpful for manually defining classes without using this structure:

type Class = setmetatable<
    {
       KeyType: ValueType;
    },
    classMeta
>;

Though, the way metatables are currently presented to the user in the type engine is with @metatable, so it may be more convenient to copy that syntax as well:

type Class = {
    KeyType: ValueType;
    @metatable classMeta;
}

[aatxe]

The main concern about @metatable would be conflicting with possible additions for attributes on types. If we pick some specific syntax for writing metatables, we would change the way it is displayed to match that.