聊天列表訊息合併，處理相鄰時間

<!-- div-->
<view v-if="setMsgTime(item.time,index > 0 ? list[index - 1].time : 0)">
        <!-- 格式化時間 根據需求顯示時間格式，這裡time 格式為時間戳-->
    {{ formatMsgTime(item.time) }}
</view>

<!-- script -->
setMsgTime(currTime, prevTime) {
    var timestampShowFlag = false;
    if (currTime <= 0) {
        timestampShowFlag = '';
    } else if (!prevTime || prevTime <= 0) {
        timestampShowFlag = true;
    } else {
        const minDiffToShow = 10 * 60; // 10min 10*60s
        const diff = currTime - prevTime; // s
        if (diff >= minDiffToShow) {
            timestampShowFlag = true;
        }
    }
    return timestampShowFlag;
}