Finish CNCF Sandbox onboarding

[hiddeco]

See cncf/sandbox#157

Individual issues on our side (but not limited to):

• Develop a process for CNCF project proposals and approval cncf/toc#1
• Add initial project proposal process cncf/toc#2
• Develop a process for Working Group formation cncf/toc#3
• Add section on TOC voting for clarity cncf/toc#4
• Clarify CNCF project acceptance criteria cncf/toc#5
• Add Working Groups proposal cncf/toc#6
• Adding CoreDNS project proposal links cncf/toc#7
• Update project proposal process to move to GitHub cncf/toc#8
• Create project proposal for CoreDNS cncf/toc#9