GitHub project mirror/host own forge

As this post (french) mention it well, GitHub is also a danger for the project if we are not prepared to its fall down or any decision of its owners.

uCoin & its other projects should have a mirror:

for example using GitLab or Gogs
with all the issues & wiki
eventually with webhooks

This does not avoid using GitHub, but we should take care to be able to push our commits, issues & wiki either in one place or the other, and this change reflected on the other platform.

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information