[Cin] Files for multi-cam

[Andrea paz]

For those who do not follow the forum: an appendix (D.2) with an
Armandux multi-cam workflow has been added to the manual. The good
thing is that it provides its multicam material (3 video tracks with
its own audio and one external audio track; all of good quality) for
anyone who wants to experiment and try multicam, but has no material
available. It's also always nice to see a magician at work!
https://www.cinelerra-gg.org/forum/forum-news/contest/