Document what flavor of regular expressions this grammar supports

[keidax]

After quickly scanning the rules, I'm guessing this is meant to parse PCRE2 or ECMAScript regular expressions. It would be helpful if the project explained this explicitly.

[amaanq]

It's a somewhat "general" regex parser, and doesn't strictly adhere to one regex flavor. There's support for PCRE2, ECMAScript, and POSIX regexes.

[amaanq]

I've just updated the docs w/ this info