Improve schema help text for Animation classes

[swashbuck]

Subject of the issue

The AAT allows you to add an animation to a block, component or article. However, the tooltip help for "Classes" does not give any indication of what classes to use.

Suggestion

It would be more user-friendly to list out the default Vanilla animation classes with the caveat that there may be additional custom classes provided by the theme. The new help text could be:

The CSS class(es) to add to the element. These include 'fade-in-top', 'fade-in-bottom', 'fade-in-left', and 'fade-in-right' as well as any custom classes supplied by the theme.

Alternatively, we could offer these 4 class options in a dropdown, but that would remove the ability to use any custom theme classes. This would be simpler for the course creator, though.

[kirsty-hames]

Alternatively, we could offer these 4 class options in a dropdown, but that would remove the ability to use any custom theme classes. This would be simpler for the course creator, though.

Hey @swashbuck, how about both? A dropdown for existing Vanilla classes and a _classes property to support custom styles.

In general for AAT, I'd like to see existing Vanilla classes in a dropdown so it's easier for course authors to see styles available and a _classes property for customisation.

[swashbuck]

@kirsty-hames Yep, sounds good to me. The best of both worlds.