Update the Wiki and make it discoverable... or else delete it

[mizmay]

Really hard to find but it's here: https://github.com/cugos/cugos.github.com/wiki/Editing-The-Website

• Update links
• Improve explanation of how to add yourself to the meetings (if you are outside the organization, it requires forking)
• Make it discoverable on the website

[mizmay]

Revising the title to reflect the option to just delete the wiki. All content on the wiki apart from stuff related to #433 is now out-of-date and conflicting, or else redundant with content on the README.md or CONTRIBUTING.md pages.