Better regexps, and new error handling

• Added error handling to LALR!

  • on_error option to Lark.parse().
    Read here: https://lark-parser.readthedocs.io/en/latest/classes/#larkparse
  • Parser now comes with a puppet for advanced error handling.
    Read here: https://lark-parser.readthedocs.io/en/latest/classes/#parserpuppet

• Support for better regexps with the regex module, when using Lark(..., regex=True)
  Read here: https://lark-parser.readthedocs.io/en/latest/classes/#using-unicode-character-classes-with-regex