Add color options to heading block.

[jorgefilipecosta]

Description

Closes: #6012

This PR adds the color options available in the Paragraph and button block to the heading block.

How has this been tested?

I verified the color options in the heading block work as expected.

[mapk]

I tested this and it worked great!

Let's merge this, but keep in mind that we may want to reevaluate the background color options for all these text blocks and just use the Group block to provide that.

[youknowriad]

But keep in mind that we may want to reevaluate the background color options for all these text blocks

Do we have a decision here, because I'd rather not introduce something that is going to be removed (it's always hard to remove things when they become APIs)

[mapk]

Do we have a decision here?

Yes, we're going to keep this in. A decision is made to keep background color on most (if not all) text blocks. #8171 (comment)

Let's merge it.

[youknowriad]

We could use an e2e test.

I wonder how much of this code could be reused across blocks.

[jorgefilipecosta]

Thank you for the reviews @youknowriad, @mapk 👍

We could use an e2e test.

I will follow up with an end 2 end test for this functionality.

I wonder how much of this code could be reused across blocks.

We already have a big amount of code reusability, by using shared components for the UI, withColors for the logic, and shared functions. But I agree it is something we could try to improve further. The main decision we would need to do would be the way this reusability would work, the simplest option would be a supports flag for color, but in previous discussions, there was no clear agreement if we should continue investing in support options.

[BinaryMoon]

We really need this for all block controls (lists, paragraphs etc). Anything that can be used on a group block with a coloured background could cause readability issues and so the text colour will need to be changeable.

[mapk]

That's the next step here, @BinaryMoon. We want to add text color options to all text blocks.

[justintadlock]

The .has-text-color class is missing. It only shows the .has-xxx-color class.

[paaljoachim]

Heading background color was removed:
#15814

With the thought that "The idea being that backgrounds should be higher-level (group block)."