API documentation fixes

Fixes:
1. `GET /api/agency/` does not display processing time or reading rooms so I fixed the example and moved the stats documentation to the `GET /api/agency/{{slug}}` section
2. Updated with Example API Call and results that reflect the current API
3. added "working" days to stats documentation. 

Should fix #333 and #366 

We can't have this URL here. It's not intended for public consumption. Please remove.