Add prometheus example queries

Author: mblaschke

README.md

@@ -120,3 +120,23 @@ Application Options:
 Help Options:
   -h, --help                                  Show this help message
 ```
+
+
+Prometheus queries
+------------------
+
+Current oncall person
+```
+pagerduty_schedule_oncall{scheduleID="$SCHEDULEID",type="startTime"}
+* on (userID) group_left(userName) (pagerduty_user_info)
+```
+
+Next shift
+```
+bottomk(1,
+  min by (userName, time) (
+    pagerduty_schedule_final_entry{scheduleID="$SCHEDULEID",type="startTime"}
+    * on (userID) group_left(userName) (pagerduty_user_info) 
+  ) - time() > 0
+)
+```