Add Ability to Control Styles on Spotlights

[kimberspencer]

Description
Add the ability to control the styles of header text, body copy and the button.

Why it's Important
Style changes to the copy/buttons allows more creative freedom when choosing bg images, can help with readability and can improve the look of spotlights.

Possible Implementation

• Add fields similar to the ucf-section plug.
• Allow html in the current header, body and button fields (it's currently getting run through sanitize_text_field so it strips html).

Additional context