Create .github repo

[vweevers]

With FUNDING (linking to OpenCollective), CODE_OF_CONDUCT and CONTRIBUTING.md.

See https://help.github.com/en/articles/creating-a-default-community-health-file-for-your-organization

Ref https://github.com/Level/community/issues/32

[vweevers]

• [x] Add FUNDING.yml
• [x] Add CODE_OF_CONDUCT.md
  • [x] Forward team@leveljs.org
• [x] Add CONTRIBUTING.md
  • [x] Copy the small style tweaks to community/CONTRIBUTING.md
• [x] Enable sponsorship buttons on all repos
• [x] Add hallmark
• [x] Add a README.md (see https://github.com/syntax-tree/.github for a good example)