Fix a couple typos (react-native-maps#1375)

Author: ryanguest

README.md

@@ -207,7 +207,7 @@ Then add the AirGoogleMaps directory:
 
 https://github.com/airbnb/react-native-maps/blob/1e71a21f39e7b88554852951f773c731c94680c9/docs/installation.md#ios
 
-An unoffical step-by-step guide is also available at https://gist.github.com/heron2014/e60fa003e9b117ce80d56bb1d5bfe9e0
+An unofficial step-by-step guide is also available at https://gist.github.com/heron2014/e60fa003e9b117ce80d56bb1d5bfe9e0
 
 ## Examples
 

lib/android/src/main/java/com/airbnb/android/react/maps/AirMapModule.java

@@ -86,7 +86,7 @@ public void execute (NativeViewHierarchyManager nvhm) {
                 view.map.snapshot(new GoogleMap.SnapshotReadyCallback() {
                     public void onSnapshotReady(@Nullable Bitmap snapshot) {
 
-                        // Convert image to requested width/height if neccesary
+                        // Convert image to requested width/height if necessary
                         if (snapshot == null) {
                             promise.reject("Failed to generate bitmap, snapshot = null");
                             return;