addDanmu method
最好按照时间顺序插入弹幕
Implementation
bool addDanmu(T model) {
assert(isEnable);
var result = _addEntry(model);
if (danmuItems.isNotEmpty && isAnimating && _status == DanmuStatus.idle) {
_status = _idleBeforeStatus;
_checkStatusChanged();
}
return result;
}