rt
请参考https://developers.weixin.qq.com/miniprogram/dev/api/canvas/Canvas.html
https://leekoho.github.io/ 参考
1.border设置三角形
2.view写个方块通过transfrom旋转只显示一个角
圆弧
1.border
2.border-radius
可参考 https://blog.csdn.net/qq_37949737/article/details/90695437