Add api routes

This commit adds in the required mediawiki extension code (namely the extension.json and i18n file) along with two API routes, HeartbeatConnected and HeartbeatFailure. Heartbeat connected returns a json response with the server time, and HeartbeatFailure makes a log in a log page to record a failure. The intention is to poll HeartbeatConnected on a regular interval, and if the request ever fails, store that failure until a successful connection is reached, and log it using the HeartbeatFailure route.