[Feature Request] Add custom themes

[sillynocodecat]

Now white theme is perfect, but black is not so comfortable for long-time visits. It would be great to add function to customize your own theme.

I think there's no need to create a big no-code parametres to customize, it would be great to load theme from .json file with parametres or smth.

I understand that your idea is bring "wysiwyg" edit for tables but with grow community I think we will see custom themes by other. And people, who can't code, will be able just to upload other .json file and see new comfort theme.