[Feature Request]: Customize base theme colors

### Guidelines

- [X] I have searched the issue tracker for [open](https://github.com/FreeTubeApp/FreeTube/issues?q=is%3Aopen+is%3Aissue) and [closed](https://github.com/FreeTubeApp/FreeTube/issues?q=is%3Aissue+is%3Aclosed) issues that are similar to the feature request I want to file, without success.
- [X] I have searched the [documentation](https://docs.freetubeapp.io/) for information that matches the description of the feature request I want to file, without success.
- [X] This issue contains only one feature request.

### Problem Description

Can you add a color picker wheel in settings to enable anyone to set his own custom color for the theme background?


### Proposed Solution

In settings there could be a custom option when you click on it a wheel with diffrent color options will appear. It would have either the RGB or HEX color options you could use your mouse to set your own color and the background would change that way. This option is the same what you set in GIMP, Krita or even in web search could you add this?

### Alternatives Considered

If a color wheel is not a option how about just a field where you can paste your own RGB or Hex color and change it to a custom background that way


### Issue Labels

improvement to existing feature, new feature, new optional setting

### Additional Information

Maybe this could also be implemented for Main color and Secondary color theme as well