Adding notes for Google Play Services (react-native-maps#2631)

Important note for Google Play Services when conflicting with other modules

Author: areeb111

docs/installation.md

@@ -412,3 +412,24 @@ import com.airbnb.android.react.maps.MapsPackage;
   are not supported by your device.`, you need to change the emulator
   CPU/ABI setting to a system image that includes Google APIs.  These may
   need to be downloaded from the Android SDK Manager first.
+  
+  
+  ### Google Play Services conflicting issues with other modules
+  
+  In case you have multiple modules using Google Play Services such as `react-native-onesignal`, Make sure to exclude all the Google Play Services dependencies from the modules and import all the Google Play Services dependencies for all the modules in the project-wide `build.gradle` file like the following example:
+  ```
+   implementation(project(':react-native-onesignal')){
+        exclude group: 'com.google.android.gms'
+    }
+    
+   implementation(project(':react-native-maps')){
+        exclude group: 'com.google.android.gms'
+    }
+    implementation 'com.google.android.gms:play-services-base:12.0.1'
+    implementation 'com.google.android.gms:play-services-basement:12.0.1'
+    implementation 'com.google.android.gms:play-services-location:12.0.1'
+    implementation 'com.google.android.gms:play-services-tasks:12.0.1'
+    implementation 'com.google.android.gms:play-services-maps:12.0.1'
+    
+    
+  ```