Add Whitespace0 and Whitespace1 combinators

[oleiade]

The library should have some version of a Whitespace0 and Whitespace1 character parser combinators.

Those combinators would consume zero or more white space characters: spaces, linefeed, carriage return, and horizontal tabs. The 1 variant would fail if at least one whitespace character failed to match.

It would likely have a prototype such as:

func Whitespace0[Input Bytes]() Parser[Input, Input]