Feat: Dynamic styles

[rodinalex]

This commit adds the feature that allows one to include
dynamic effects, such as hover and pressure, to the
style options. The user is able to add his or her own
effects using the JS events. The syntax is closely linked
to the original Styles library.

I have added the comments, but they do not seem to compile
correctly. I would really appreciate some help with that.
Thank you.

[seanhess]

Hi @rodinalex, I would recommend using https://github.com/rtfeldman/elm-css instead of this library. I'll merge this if you can figure out how to get it compiling, but otherwise, elm-css does everything this library does, and better.

[rodinalex]

Thanks for the pointer! I didn't know about that library.
I've been using your library for a project I'm working on and it's great! Thank you for putting it together.
I just updated the PR and the comments seem to be working now.