No docs on creating custom workers

[MattNot]

Hi! I was working on my editor and now i need to use an ANTLR4 parser on it.
I was following this guide made by a guy in the ANTLR docs but i made the mode like described here in your faq.
Where should i put:

1. The creation of the worker (let Worker...)
2. The "base code" of the worker

thanks for helping