[UX] CKEditor - Provide default styles

Description of the need Make it easier for new users to figure out how to edit the styles menu option in CKEditor.

I just spent a few hours trying to figure out how to get this to work. In the end, my problem was silly human error in that I was trying to get an h1 style to work while h1 were not listed as part of the allowed HTML tags for that text format. But, having default styles available at the start, would have made it much easier for me to see that they were working and to have debugged my problem. Having no styles available left me with the impression that the feature might be broken and discouraged me from even trying to find the problem.

Not having any default styles to start with seems very counter-intuitive to me.

Here is an issue I opened while trying to figure this out: https://github.com/backdrop/backdrop-issues/issues/4232

Proposed solution Provide some default styles in styles list for the Filtered HTML text format.

These could be added in the install profile to make the styles menu useful out of the box, but mostly to demonstrate to new users how it works and make it easier for people to figure out how to edit them.

Just need to figure out what some sensible styles would be to provide by default. Keep in mind, that they styles menu is not even available by default. So these default styles would only be used or even visible if a user tried to add this option to their WYSIWYG menu.

Alternatives that have been considered Related issues (some of which might mitigate need for this): https://github.com/backdrop/backdrop-issues/issues/1520 https://github.com/backdrop/backdrop-issues/issues/2980

An alternative would be to include a "No styles configured" message under the styles menu in the WYSIWYG if the styles menu is enabled, but not configured.

Additional information

This is what you see in the WYSIWYG after adding the styles option to the toolbar (but before adding any custom styles).

Once you click on it, you get an empty box - this feels very broken.