[CrashManager] Add link to query interface and document it

[choller]

[choller]

The interface lives here: /crashmanager/crashes/query/

Example URL: /crashmanager/crashes/query/?query={%22op%22:%22AND%22,%22tool__name__contains%22:%22LangFuzz%22,%22notUnboxedArrays%22:{%22args__contains%22:%22--unboxed-arrays%22,%22op%22:%22NOT%22},%22noBugOnFile%22:{%22bucket__bug__isnull%22:%221%22,%22bucket__isnull%22:%221%22,%22op%22:%22OR%22},%22crashAddressNumeric__gte%22:%2216%22}