[Cin] About links to cin-cv repos

[Andrea paz]

About page

I would make these additions (replacing the "Update:" paragraph):

"
Update: A new site for Cinelerra-CV was created on July 1 2020. There
is also a new repository and mailing list:
Website: http://cinelerra-cv.wikidot.com/
Repository: https://github.com/cinelerra-cv-team/cinelerra-cv
Mailing-list archive: https://www.freelists.org/archive/cinelerra-cv-team/
Old mailing-list archive: https://lists.cinelerra-cv.org/pipermail/cinelerra/
"