Block Editor: Add README for PanelColorSettings component

[tyxla]

What?

This PR adds a README for the PanelColorSettings component.

Fixes #52064.

Why?

Part of #22891 where we aim to document all block editor components.

How?

Just adding a README.

Testing Instructions

Not needed.

Testing Instructions for Keyboard

None.

Screenshots or screencast

None.

[mburridge]

This is great. Thanks @tyxla. The only thing I would add, if possible, is a screen shot showing the component. Quite a few of the readme's have a screen shot, such as the Block Card component.

Admittedly quite a few don't have a screen shot, so it's fine without, but I think it's a "nice to have". Feel free to merge either way.

Thanks again.

[tyxla]

The only thing I would add, if possible, is a screen shot showing the component. Quite a few of the readme's have a screen shot, such as the Block Card component.

Admittedly quite a few don't have a screen shot, so it's fine without, but I think it's a "nice to have". Feel free to merge either way.

Thanks for pointing that out. I'd say I intentionally didn't add a screenshot here since this is an adapter component - it doesn't do much more than reorganize the props and pass them down to PanelColorGradientSettings. The visual part comes from the underlying PanelColorGradientSettings, and if we're to add a screenshot, we should add it under that one's README.