Faucet website testing

[Mirko-von-Leipzig]

There have been several faucet website bugs recently (caused by me) e.g. #671, where various parts of the website aren't served.

It would be nice to test that the website loads correctly. At the moment this isn't trivially possible without actually running the full faucet, which in turn requires a full node.

Ideally the test would be self-contained, i.e.:

• serve the website (using a single method to add the route(s), which is then also used in prod)
• load the website and ensure it loads without errors

The latter would require providing a stub API expected by the webpage.

[Mirko-von-Leipzig]

@igamigo this could also be a starting issue; quite self-contained to the faucet.