[TYPO3-doc] Encouraging people to contribute with Github

[Fabien Udriot]

Just wanted to give a conclusion / wrap up to this discussion (if someone find it interesting enough).

To sum it up, nothing will change in a close future (at least not from me). With the move to Github,
it seems we would loose some integration in the commit message for cross-linking ticket(?). I
haven't understood the exact details (and it does not matter for now). Also, there were some worries
raised related Github copyright which could be workaround by keeping a backup on t3 infrastructure
as a response.