Switch Docs to MYST

[ianhi]

Problem

MYST is good stuff and probably the future so we should move to it.

Suggested Improvement

Swap to MYST. See explanation from @redeboer at #203 (comment)

[redeboer]

The conversion can be done easily with https://rst-to-myst.readthedocs.io. I could get do that later this week, have done that transition before.