Add community activities to membership requirements

[svrnm]

This updates the membership requirements to reflect that we have SIGs who express their contributions to the community outside of GitHub, and especially by organizing activities.

I think there are other parts of that document that require refinement but this is a starting point

[jack-berg]

@jack-berg, based on the comments at a PR of yours about spec sponsors, do you think we need an extra point here about SIGs that are being formed?

I don't think so actually. There's an entry in the set of possible contributions which describes SIG work as contributions:

Contributing to SIGs, subprojects, or community discussions (e.g. meetings, chat, email, and discussion forums)

I think this means that SIG work counts towards contributions from the perspective of being a spec sponsor.

[svrnm]

Contributing to SIGs, subprojects, or community discussions (e.g. meetings, chat, email, and discussion forums)

I think this means that SIG work counts towards contributions from the perspective of being a spec sponsor.

Just as a note on that: while we have this written down, we still make use of CNCF DevStats to figure out if someone is a "member of standing" for example, that's why I am a big fan of the end user, mainframe and security SIG to have their own repositories to put down some of their work, as it is tracked through DevStats.