Rename FirebaseAISample to FirebaseAIExample and update README (#1716)

* update readme.md for name changing

* update path suffix for all submodules

* change name from Sample to Example in acutal code

* Update README.md

Author: YoungHypo

firebaseai/ChatSample/Assets.xcassets/AccentColor.colorset/Contents.json renamed to firebaseai/ChatExample/Assets.xcassets/AccentColor.colorset/Contents.json

@@ -85,7 +85,7 @@ struct ConversationScreen: View {
         }
       }
     }
-    .navigationTitle("Chat sample")
+    .navigationTitle("Chat example")
     .onAppear {
       focusedField = .message
     }

firebaseai/ChatSample/Assets.xcassets/AppIcon.appiconset/Contents.json renamed to firebaseai/ChatExample/Assets.xcassets/AppIcon.appiconset/Contents.json

@@ -91,6 +91,6 @@ struct ErrorView: View {
       ErrorView(error: errorPromptBlocked)
     }
     .listStyle(.plain)
-    .navigationTitle("Chat sample")
+    .navigationTitle("Chat example")
   }
 }