Create a server-based Babel Explorer

[gaurav]

Development of a GitHub Pages version of Babel Explorer is coming along well: https://translatorsri.github.io/babel-explorer/

But we should also build a server-based Babel Explorer that would allow us to:

• Expose all the Babel Xref tools, so that the files can be downloaded to the server.
• Add a BabelTests dashboard: ideally, this would show the current status (and let you test them against any endpoints), but also show you some kind of history of previous test and coverage and so on.
  • My initial plan was to do this in GitHub Pages, which would certainly be useful for one-off testing. But making people run all the tests every time they want to look at the result seems annoying.
• Some kind of a dashboard for making sense of logs (perhaps combined with live data).