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 #32

[vweevers]

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