Add Prometheus Middleware to Router to add HTTP Metrics

[SeamusGrafana]

Somewhere between v0.11.0 and v0.12.0 the HTTP Metrics in Prometheus (such as http_request_duration_seconds_bucket and http_requests_total were missing and no longer show.

It looks like the Router no longer had the Prometheus Middleware Included so it was not generating these.

This re-adds that configuration to generate the Metrics again.

[federicotdn]

Hi, I've fixed this by changing how Quickpizza installs chi middleware, before it was using a strange combination of .Use() and .With() that broke stuff. I'll push this to production soon but it's already in dev.