add lottie animation for typing indicator

pubspec.yaml

@@ -32,6 +32,7 @@ dependencies:
   mime: ^0.9.6+3
   visibility_detector: ^0.1.5
   http_parser: ^3.1.4
+  lottie: ^0.7.0+1
   substring_highlight: ^0.1.2
   flutter_slidable: ^0.5.4
   carousel_slider: ^2.2.1
@@ -47,6 +48,7 @@ flutter:
     - images/
     - svgs/
     - lib/svgs/
+    - animations/
 
 dev_dependencies:
   pedantic: ^1.9.0