Update accessibility overview so it can be used to measure compliance support

[mrosvik]

We need to update this overview:
https://github.com/digdir/designsystemet/wiki/Accessibility-(Draft)

The goal is for the page to be used as a tool to measure which accessibility requirements Designsystemet supports in relation to compliance with universal design / accessibility regulations. This page will be linked from the benefit realization plan (Gevinstrealiseringsplan) and therefore needs to be accurate and clear.

• The list should clearly show which requirements in the regulations Designsystemet supports, and how it contributes to meeting them.
• The structure should make it easy for users to understand which requirements are relevant and which are not.