Document getCurrentConnections monitor method

Docs: Document getCurrentConnections monitor method

Author: LaravelFreelancerNL

docs/monitor-manager.md

@@ -10,4 +10,12 @@ Get Prometheus metrics of the server
 
 ```
 $arangoClient->monitor()->getMetrics();
-```
+```
+
+
+### getCurrentConnections(): int
+Get the total number of active connections (HTTP/1.1 & HTTP/2 combined)
+
+```
+$arangoClient->monitor()->getCurrentConnections();
+```