Hello, everypony! There is my test and first plugin.
Usage:
[b]cat[/b] to <b>cat</b>
[i]cat[/i] to <i>cat</i>
[link=scirra.com]Best website[/link] to <a href="https://www.scirra.com">Best website</a>
cat[/color] to <font color="orange">cat</font>
[/code:17mk1coy]
First version
https://nofile.io/f/meFFzwyRj2h/bbcode.zip
Demo
http://easybbcat.bitballoon.com