Support image sequence or mp4 for background

Vantage Requests
1

Vantage can be the best software to camera match and merge real footage with cg

Submitted on AHA Ideas (VANTAGE-I-41).

2

Removing the Shadow catcher part as they are 2 separate features and it already exists as https://chaosvantage.ideas.aha.io/ideas/VANTAGE-I-22

Submitted on AHA Ideas.

3

AHA Ideas status: Planned.
Set during AHA Ideas to Discourse migration.