高德2D地图插件
本插件主要服务于 flutter_deer。仅保持现有功能，没有的功能可自行拓展。
退回到9e1d22ec786494949637212e8cf3d4d8a1a27f94提交，曼凯App使用
Copyright 2019 simplezhli
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.