Support .env asset

Author: PrimozRatej

assets/opener_animation.riv renamed to assets/animations/opener_animation.riv

@@ -8,8 +8,8 @@ class StorageKeys {
 class Assets {
   static String logo = "assets/images/logo.png";
   static String helpImg = "assets/images/help.png";
-  static String openerAnimationForward = "assets/opener_animation.riv";
-  static String openerAnimationReverse = "assets/opener_animation_reverse.riv";
+  static String openerAnimationForward = "assets/animations/opener_animation.riv";
+  static String openerAnimationReverse = "assets/animations/opener_animation_reverse.riv";
 }
 
 class HumhubTheme {

assets/opener_animation_reverse.riv renamed to assets/animations/opener_animation_reverse.riv

@@ -94,6 +94,7 @@ flutter:
     - assets/
     - assets/images/
     - assets/images/locale/
+    - assets/animations/
   # To add assets to your application, add an assets section, like this:
   # assets:
   #   - images/a_dot_burr.jpeg