Go through wiki.docs and pull out any missing gems

[laurenluz]

Before we do this: #349
Let's do one final pass of the wiki and pull out any things we don't want to lose

[laurenluz]

Ok so I went through the wiki and I think we're almost cool to just take it down fully. Found only a few things we should still add to our docs, some of which we have issues for... They are below....

To add to docs:
Giveth calendar (at least a link)
Intro to Giveth.io
Governance process @divine-comedian https://wiki.giveth.io/dac/approved-policies/ #343
Code of Conduct @laurenluz https://wiki.giveth.io/governance/codeofconduct/ #342
Contributors Guide @WhyldWanderer https://wiki.giveth.io/dac/contributors-guide/ #347