Add android documentation

Author: Renarde-dev

docs/Architecture.md

@@ -3,6 +3,21 @@
 This file document the different directory of this project.
 Each section will contain explanation and a directory tree.
 
+## Android :
+
+The android directory contain all elements necessary to target Android, most of it is gradle configuration.
+Upgrading the `AGP (Android Gradle Plugin)` open the `android` directory with Android Studio and use **Tools > AGP Upgrade Assitant** or manually update the gradle configuration at your own risk.
+
+```
+.
+└── android
+   ├── app
+   ├── build.gradle
+   ├── gradle/wrapper/gradle-wrapper.properties
+   ├── gradle.properties
+   └── settings.gradle
+```
+
 ## Translations :
 
 Translations are hosted on [crowdin](https://crowdin.com/project/piwigo-ng), everything is translated from english.