README: Added badge link to the app store app page

README.rst

@@ -3,6 +3,9 @@ Vector-ios
 
 Vector/iOS is an iOS Matrix client. 
 
+.. image:: https://linkmaker.itunes.apple.com/images/badges/en-us/badge_appstore-lrg.svg
+   :target: https://itunes.apple.com/us/app/vector-open-source-collaboration/id1083446067?mt=8
+
 It is based on MatrixKit (https://github.com/matrix-org/matrix-ios-kit) and MatrixSDK (https://github.com/matrix-org/matrix-ios-sdk).
 
 You can build the app from source as per below:
@@ -31,4 +34,4 @@ Licensed under the Apache License, Version 2.0 (the "License"); you may not use
 
 http://www.apache.org/licenses/LICENSE-2.0
 
-Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.
+Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.