Look into Pa11y accessibility checks

Came across in CfRR when made pull request, ran their action -

https://github.com/coding-for-reproducible-research/CfRR_Courses/blob/main/.github/workflows/accessibility.yml

https://github.com/coding-for-reproducible-research/CfRR_Courses/blob/main/.github/workflows/accessibility_complete.yml

Runs Pa11y - https://pa11y.org/ - a free and open source tool to help make web pages more accessible.