Add fancy_regex support

[stevefan1999-personal]

Fixes #3

[igordejanovic]

Looks good. Thanks. Would you be able to add a test for this feature?

[stevefan1999-personal]

Looks good. Thanks. Would you be able to add a test for this feature?

Oh I think it is out of the box compatible with the original regex so it is not that needed.

I have literally used the fancy-regex's main page example to parse Rust raw string: r(#*)".*?"\2. There is a slight change because the regex itself is wrapped in a main capture group, so it ended up being (r(#*)".*?"\1) internally in the generated lexer, which is obviously incorrect and so I fixed the capture cardinal to 2,

[igordejanovic]

I've made a little test nevertheless just to be sure that it keep working as intended. I've stumbled across the same problem with capture groups so I removed wrapping in outer parentheses which should now work most of the time except for situation like a|b which should be written as (a|b) or a|^b (this should be noted somewhere in lexer docs probably). I also added fancy regex config to CLI.