Init a docs section for monitoring, document queue-runner-status and the prometheus metrics

Dependencies

• [2] 3JXCTKEC Add markdown files for documentation

Change contents

• edit in doc/manual/src/SUMMARY.md at line 7
  [2.290]

  [2.290]
  + - [Monitoring Hydra](./monitoring/README.md)
• file addition: monitoring (d--r------)
  [2.99]
• file addition: README.md (----------)
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  + # Monitoring Hydra

  +

  + ## Webserver

  +

  + The webserver exposes Prometheus metrics for the webserver itself at `/metrics`.

  +

  + ## Queue Runner

  +

  + The queue runner's status is exposed at `/queue-runner-status`:

  +

  + ```console

  + $ curl --header "Accept: application/json" http://localhost:63333/queue-runner-status

  + ... JSON payload ...

  + ```

  +