First off, great library, thanks for putting it together!

After some initial and very promising setup using rust-peg for the first time, I'd like to have a clearer path regarding possible modularization capabilities, e.g, to have my main grammar defined from sub-grammars defined in other modules. What would be the mechanism and/or best practice to accomplish that? Though #25 seems relevant, it's from several years ago, and I'm having trouble following the discussion there. Anyway, I thought I'd add an entry here hoping to gather some "fresh" insights about this modularization aspect. Thanks.