implement no-empty-character-class

[Kelbie]

Hi, this is my first serious pull-request on an open-source project so I'd appretiate any feedback you could give.

I implemented all the same tests that eslint has with some modification because the rome linter was complaining.

The regex I used for checking if there is an empty character class is /^([^\\[]|\\.|\[([^\\\]]|\\.)+\])*$/u which comes from the eslint regex: /^\/([^\\[]|\\.|\[([^\\\]]|\\.)+\])*\/[gimuys]*$/u. I trimmed it down because in rome it's testing the pattern and in eslint it's testing the full regex.

#94

[sebmck]

Looks good! Could you format the files with prettier? scripts/prettier-format will do it for you.

[sebmck]

I would love to add a regex parser and enrich the RegExpLiteral node. It would allow a ton of amazing transforms and lints. Hopefully if we can make this happen this lint can be a whole lot simpler and more reliable. Thank you for the PR!