added fdroid flavour (#3)

android/app/build.gradle

@@ -44,6 +44,24 @@ android {
         versionCode flutterVersionCode.toInteger()
         versionName flutterVersionName
         testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
+    
+    }
+
+    flavorDimensions "deploy"
+
+    productFlavors {
+        fdroid {
+            dimension "deploy"
+            signingConfig null
+        }
+    }
+
+    android.applicationVariants.all { variant ->
+        if (variant.flavorName == "fdroid") {
+            variant.outputs.all { output ->
+                output.outputFileName = "app-fdroid-release.apk"
+            }
+        }
     }
 
     buildTypes {