Switch recommonmark to myst-parser

recommonmark is being phased out in favor of myst-parser, see Proposal to sunset recommonmark in favor of MyST-Parser · Issue #221 · readthedocs/recommonmark · GitHub . Feedback on the transition would be useful to the maintainers on that issue.

Thx for letting us know! I added an issue to the backlog of the infrastructure working group. Not sure if that is in scope for that group…