Allow Solid CG PRs to be reviewable by anyone or at minimum allow Solid CG participants to review

[csarven]

It seems to be that PR reviews are limited to Solid org Members.

That list does not include every Solid CG participant.

Consider TODOs:

• Solid CG PRs must be reviewable by Solid CG participants.
• Solid CG PRs should be reviewable by anyone in public.

Consider also:

• Migrate all CG assets to W3C space w3c-cg/solid#79

[csarven]

If the Solid CG doesn't have strong reasons against allowing anyone to share a public review on Solid CG PRs, then we should make sure that it is possible. If the Solid CG has reasons against, lets record them.