Add color option for Headings

[stefan-cotitosu]

What problem does this address?

A customer replying to our NPS emails shared more insights, including the fact that for each Heading tag, there should be a color option available, that applies sitewide.

What is your proposed solution?

In the Colors panel, we can add a section to add color control for each type of Heading.

Reported here: https://secure.helpscout.net/conversation/2472678838/399453?viewId=212385

Will this feature require documentation? (Optional)

No.

[lmisch]

+1

[mghenciu]

+1 on this.

But I think initially just having 2 colors (1 for headings and 1 for body) should be fine.

I was working on the new demo, and wanted to have the headlines dark, but body text to use a more subtle color.
Currently this is not possible.

Another example is WPShout, where we also use a stronger color for the headings and something more dimmed for the body.