Onetap V4 documentation added

Onetap V4 documentation has been added!

There are probably still some changes that I missed, so hit me up on my discord in the #docs channel.

Sources

• V4 Runtime dump by sorry#1337 from 03-04-2021
  • On my discord: message
• april's documentation
  • old V3 documentation on UI module
• user snippets by weiz#8672 from 05-02-2021
  • Javascripting discord: message
• limited dump of the official docs