Added fastlane, updated instructions on generating files

android/app/build.gradle

@@ -25,6 +25,12 @@ apply plugin: 'com.android.application'
 apply plugin: 'kotlin-android'
 apply from: "$flutterRoot/packages/flutter_tools/gradle/flutter.gradle"
 
+def keystoreProperties = new Properties()
+def keystorePropertiesFile = rootProject.file('key.properties')
+if (keystorePropertiesFile.exists()) {
+    keystoreProperties.load(new FileInputStream(keystorePropertiesFile))
+}
+
 android {
     compileSdkVersion 33
 
@@ -42,7 +48,6 @@ android {
     }
 
     defaultConfig {
-        // TODO: Specify your own unique Application ID (https://developer.android.com/studio/build/application-id.html).
         applicationId "de.astubenbord.paperless_mobile"
         minSdkVersion 21
         targetSdkVersion flutter.targetSdkVersion
@@ -50,13 +55,20 @@ android {
         versionName flutterVersionName
     }
 
-    buildTypes {
-        release {
-            // TODO: Add your own signing config for the release build.
-            // Signing with the debug keys for now, so `flutter run --release` works.
-            signingConfig signingConfigs.debug
-        }
-    }
+   signingConfigs {
+       release {
+           keyAlias keystoreProperties['keyAlias']
+           keyPassword keystoreProperties['keyPassword']
+           storeFile keystoreProperties['storeFile'] ? file(keystoreProperties['storeFile']) : null
+           storePassword keystoreProperties['storePassword']
+       }
+   }
+   buildTypes {
+       release {
+           signingConfig signingConfigs.release
+       }
+   }
+
 }
 
 flutter {