Add typing to Scanner

[Alunderin]

Changes state_inline.Scanner into a typing.NamedTuple instead of a collections.namedtuple. They should be functionally equivalent except that the former has typing for its members while the latter does not.

I tend to use strict type checking for my own projects so it'd be nice if Pyright didn't freak out when I try to access the result of scanDelims without using typing.cast.