Add "min requirements" for websites based on proj maturity level

[chalin]

• Closes #30
• Closes #79
• Is based on discussions with @celestehorgan

Preview:

• https://github.com/chalin/techdocs/blob/chalin-okr-4-2-2021-11-03/assessments/criteria.md#minimal-website-requirements
• https://github.com/chalin/techdocs/blob/chalin-okr-4-2-2021-11-03/assessments/template.md#website

[chalin]

Thanks for the approvals! Merging.