bump version to 21.0.0 Alpha 1

Signed-off-by: Marcel Hibbe <dev@mhibbe.de>

app/build.gradle

@@ -40,8 +40,8 @@ android {
 
         // mayor.minor.hotfix.increment (for increment: 01-50=Alpha / 51-89=RC / 90-99=stable)
         // xx   .xxx  .xx    .xx
-        versionCode 200010015
-        versionName "20.1.0 Alpha 15"
+        versionCode 210000001
+        versionName "21.0.0 Alpha 1"
 
         flavorDimensions "default"
         renderscriptTargetApi 19