Add IzzyOnDroid download badge

Author: ofalvai

README.md

@@ -1,6 +1,6 @@
 # Habit Builder [![Build Status](https://app.bitrise.io/app/956ea5e751ec6be4/status.svg?token=WbwlLF41eOlFjQWJ5WFEMw&branch=main)](https://app.bitrise.io/app/956ea5e751ec6be4)
 
-[<img src="https://user-images.githubusercontent.com/1694986/111364968-24a0fa00-864f-11eb-88aa-4b4127d8e012.png?width=100" width="200"></img>](https://play.google.com/store/apps/details?id=com.ofalvai.habittracker)
+[<img src="https://user-images.githubusercontent.com/1694986/111364968-24a0fa00-864f-11eb-88aa-4b4127d8e012.png?width=100" width="200"></img>](https://play.google.com/store/apps/details?id=com.ofalvai.habittracker) [<img src="https://gitlab.com/IzzyOnDroid/repo/-/raw/master/assets/IzzyOnDroid.png" width="200"></img>](https://apt.izzysoft.de/fdroid/index/apk/com.ofalvai.habittracker/)
 
 ![Header](docs/feature_graphic.png)
 
@@ -73,4 +73,4 @@ This project is also a testing ground for new technologies I'd like to explore.
    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.
-```
+```