Determine If Main Media Captions on Galleries and Immersives Should Include "Main Image:"

[JamieB-gu]

On immersives and galleries, at narrower breakpoints, the caption for the main media appears below the standfirst. On frontend, at these narrower breakpoints, "Main image: " is prepended to the caption text, but this is not the case on DCAR-rendered immersives or galleries. Speak to Design and @paperboyo about whether to reintroduce this.

Note: Main media may not be an image on immersives, so "Main image:" may not always be the correct copy there.

Additional note from @paperboyo : Maybe standardise to camera icon in this scenario (remember to remove it in empty caption+Display credit:OFF case)

Frontend	DCAR

[ioannakok]

Designs by @richcousins: https://www.figma.com/design/yXvqv6fZP5uxfBhAmEFBV3/Webex-Tools-Product-Discovery?node-id=183-901&p=f&t=Dnw00FCZMV29ts2W-0