Revert "Remove Android Auto support (for now)."

This reverts commit 6c2adfeec2.

app/src/main/AndroidManifest.xml

@@ -107,6 +107,9 @@
     <meta-data android:name="com.google.android.gms.version"
                android:value="@integer/google_play_services_version" />
 
+    <meta-data android:name="com.google.android.gms.car.application"
+               android:resource="@xml/automotive_app_desc" />
+
     <meta-data android:name="firebase_analytics_collection_deactivated" android:value="true" />
     <meta-data android:name="google_analytics_adid_collection_enabled" android:value="false" />
     <meta-data android:name="firebase_messaging_auto_init_enabled" android:value="false" />

app/src/main/res/xml/automotive_app_desc.xml

@@ -0,0 +1,3 @@
+<automotiveApp>
+   <uses name="notification"/>
+</automotiveApp>