Update READMEs to reflect template changes

[jmbowman]

The README generated from frontend-template-application has been updated in openedx/frontend-template-application#585 to reflect standards decided on as part of the maintainership pilot. Most of these changes will also be needed in the README for each MFE in the openedx GitHub org, and some will also be needed for the ones in the edx org. If there are questions about which changes are applicable for each repo, please ask @nedbat, @feanil, or @arbrandes .