新增一個POPCover

<div class="send-block">
          <div class="tool-bar">
              <el-popover
              placement="top-start"
              title="選擇表情符號"
              width="200"
              trigger="click"
              content="☹️☹️☹️☹️☹️">
              <span class="emoji-button" slot="reference" circle size="small">?</span>
            </el-popover>
          </div>
           <textarea class="input" @keyup.enter="sendMessage" v-model="newMessage">
           </textarea>
        </div>

插入所選中的Emoji