JSON is a very human-unfriendly format; that makes editing JSON pages, especially JSON pages with free text (e.g. the description field in EventLogging schemas, which tends to be very long and have newlines and quotation marks) cumbersome. We should support YAML as an alternative format.

This could happen in the form of a separate YAML content type (and then extensions would be updated to accept that alongside JSON), or the JSON content type could allow for YAML storage and somehow convert it transparently (although that seems fragile), or maybe YAML could be handled purely on the editor level, like how VisualEditor handles the WYSIWYG HTML (although that would assume JSON -> YAML conversion can be done in a useful way, which is probably not the case).