Document additional API endpoints

[tomberek]

The /job/{project-id}/{jobset-id}/{job-id}/shield endpoint exists and is referenced in https://github.com/NixOS/hydra/blob/master/hydra-api.yaml . There are several others that currently work, but are not included in the YAML.

• /job/{project-id}/{jobset-id}/{job-id}/build-times
• /job/{project-id}/{jobset-id}/{job-id}/closure-sizes
• /job/{project-id}/{jobset-id}/{job-id}/output-sizes
• /job/{project-id}/{jobset-id}/{job-id}/latest (via a redirect)

Additionally, one would imagine /job/{project-id}/{jobset-id}/{job-id} would offer a list. The /all?page=N endpoint does not accept an application/json output at the moment.

A few more:

• /metrics
• /queue-runner-status