Custom Theming

[MrDogeBro]

This would add the ability to add custom themes. These themes would be themes that user can create. They would be based off of one of the existing themes. This would make sure that if a theme were to be missing any part of it, it would just revert that part back to the default for the base theme.

As a part of custom themes, there would also be support for community themes. There would be a system put into place that would allow people to create custom themes and publish them. These themes could then be used by other people via the extension, which would make it easy to do for both sides. This would allow users of the extension to include themes that were built by others in their docs.