Setup docs website for accessibility audit

[pavithraes]

📌 Summary

@frankelavsky is working on the initial accessibility audit for Bokeh and documenting finding in https://github.com/Quansight-Labs/bokeh-a11y-audit

It will be helpful to setup a docs website to present the audit process and findings. It will provide better navigation and search options, as well as allow us to include videos in the docs (solving Quansight-Labs/bokeh-a11y-audit#3)

🔖 Tasks to complete

• Setup a Sphinx-based docs website, that uses PyData Sphinx Theme
• Deploy the website with Read The Docs, with PR previews enabled
• Setup docs-health tools like pre-commit formatting

🔍 Acceptance Criteria

We have a deployed website where all the audit finidngs can be accessed.