Multi GCS: include multi_gcs.md in en/SUMMARY.md and en/README.md

Author: Davidsastresas

en/SUMMARY.md

@@ -81,5 +81,6 @@
   * [Traffic Management (UTM/ADS-B)](services/traffic_management.md)
   * [Events Interface (WIP)](services/events.md)
   * [Time Synchronization](services/timesync.md)
+  * [Multi GCS Control Protocol](services/multi_gcs.md)
 * [Contributing](contributing/contributing.md)
 * [Support](about/support.md)

en/services/README.md

@@ -42,3 +42,4 @@ The main microservices are shown in the sidebar (most are listed below):
 - [Events Interface (WIP)](../services/events.md)
 - [Time Synchronization](../services/timesync.md)
 - [Illuminator Protocol](../services/illuminator.md)
+- [Multi GCS Control Protocol](../services/multi_gcs.md)