xo-tokenizer documentation

xo-tokenizer provides a tokenizer for the Schematika language.

Syntax is generally C-like, but with some important differences. Notably, characters used for arithmetic operators (+, -, *, /) may appear in variable names: one-of-those-days is an ordinary symbol.

Typically applications would use xo-reader to construct Schematika expressions instead of interacting directly with xo::scm::tokenizer.