Board Decisions/20191219-001-List of decisions

Matter
https://mail.jabber.org/pipermail/members/2019-December/009055.html

keep a public list of Board decisions, on our wiki, using identifiers that help finding context (much) later.

Context
Lots of the XSF process, apart from what appears in the bylaws is undocumented. This is an effort to change this bad habit.