ref(chat): change input placeholder

lang/main.json

     },
     "chat": {
         "error": "Error: your message \"__originalText__\" was not sent. Reason: __error__",
-        "messagebox": "Enter text...",
+        "messagebox": "Type a message",
         "nickname": {
             "popover": "Choose a nickname",
             "title": "Enter a nickname to use chat"

react/features/chat/components/web/ChatInput.js

 import Emoji from 'react-emoji-render';
 import type { Dispatch } from 'redux';
 
+import { translate } from '../../../base/i18n';
 import { connect } from '../../../base/redux';
 
 import { sendMessage } from '../../actions';
     /**
      * Optional callback to get a reference to the chat input element.
      */
-    getChatInputRef?: Function
+    getChatInputRef?: Function,
+
+    /**
+     * Invoked to obtain translated strings.
+     */
+    t: Function
 };
 
 /**
                 </div>
                 <div className = 'usrmsg-form'>
                     <textarea
-                        data-i18n = '[placeholder]chat.messagebox'
                         id = 'usermsg'
                         onChange = { this._onMessageChange }
                         onKeyDown = { this._onDetectSubmit }
-                        placeholder = { 'Enter Text...' }
+                        placeholder = { this.props.t('chat.messagebox') }
                         ref = { this._setTextAreaRef }
                         value = { this.state.message } />
                 </div>
     }
 }
 
-export default connect()(ChatInput);
+export default translate(connect()(ChatInput));