VIP: .vyi files

[fubuloubu]

should it look more like this?

@external
def my_method(foo: DynArray[uint256, ...]):
    ...

where ... is the actual Python elipsis AST node and represents letting the downstream use case decide what the value is that goes there

[charles-cooper]

dropping this here because it seems related #1944

[charles-cooper]

i like the use of ellipses - also to mark the body of the function as unimplemented (which can be a syntactic difference between .vyi and .vy files)

[charles-cooper]

done in #3663