[x] Remove random list of (previously) online databases
[x] Add mention of providers dashboard
[x] Add "Get Involved" section
[x] Advertise meetings
[x] Advertise workshop
[x] Advertise mailing list
[x] Advertise
[x] Add a bunch of random people to CODEOWNERS so they get automatic review requests
This PR does not:
improve the wording of the intro paragraph that describes what OPTIMADE is, potentially separating the motivation section to a new page as suggested at #9. It would be good if this could be added to the README of the specification too.
This PR refactors the index page of the website:
This PR does not: