TF-46 Compose email from ThreadView

lib/features/thread/presentation/thread_view.dart

@@ -42,6 +42,12 @@ class ThreadView extends GetWidget<ThreadController> {
           )
         )
       ),
+      floatingActionButton: FloatingActionButton(
+        elevation: 0.0,
+        child: new Icon(Icons.add),
+        backgroundColor: AppColor.appColor,
+        onPressed: () => controller.composeEmailAction()
+      )
     );
   }