Swap background video with image on mobile devices (and vice versa)

[StrangeTech]

@Marius, bug raised for the background source tab:

Include background source tab when editing relative styles

Description: When editing a relative style, we are not able to edit the background image source, even though the image size and position can be edited. Step-by-step reproduction instructions: Open the Post Editor/Site Editor Add any block Add a relative style to the block Go to the Design > Background tab Notice there is no Source tab available. Screenshots, screen recording, code snippet This is the source tab on a normal block: [Screenshot 2023-04-11 at 21.00.38] This is what we see o…