Document support channels

[justinwb]

Document support channels (gitter, email, github) in github repository and on main page at solidcommunity.net.

[bourgeoa]

• gitter is a good idea because of the direct link to issues and PR

• I'd like to have wiki support activated on github for FAQ help desk and server documentation.

• email could be used on major version changes or urgency like solid.community to solidcommunity.net
  it is a high load for current operations.
  Some kind of notifications inside the popup login , the mashlib current page and the server page should be enough

[ewingson]

@bourgeoa I thought I leave this https://unix.stackexchange.com/questions/374852/create-file-using-wildcard-in-absolute-path for reference. of course we' d have to adjust the script (it' s just for the principle)...