Port Regex from original flapjs

[Lexseal]

The original flapjs has an excellent regular expression implementation. This module can be reused. Additionally, take a look at the frontend for this module and see what can be ported.

If you think you can do one better, you can write something from scratch.

Edit: Also design a regex to DFA/NFA functionality. There are existing algos one can follow. We might want to scramble the states so people cannot use them to cheat.