fix: PendingMsg is missing isUserMessage method(#695)

If you spread message object in reducer, it will loose
some methods such as `isUserMessage` `isFileMessage` etc

Fixes: https://sendbird.atlassian.net/browse/CLNP-523

Author: Sravan S

src/modules/Channel/context/dux/reducers.js

@@ -146,7 +146,9 @@ export default function reducer(state, action) {
         ...state,
         allMessages: [
           ...state.allMessages,
-          { ...action.payload },
+          // Message should not be spread here
+          // it will loose some methods like `isUserMessage`
+          action.payload,
         ],
       };
     case actionTypes.SEND_MESSAGEGE_SUCESS: {