[Topic] WCAG and compliance

[rianrietveld]

URL: https://wpaccessibility.org/docs/topics/wcag/
Code: https://github.com/wpaccessibility/wp-a11y-docs/blob/main/docs/topics/wcag/index.md

Please read How to contribute before you start.

Tasks

This content should be reviewed and expanded and maybe divided into separate topics.
Do we have a baseline for WordPress? See also "Discussion" on #92.