版本：4.0.5
- https://cdn.bootcdn.net/ajax/libs/signature_pad/4.0.5/signature_pad.js
- https://cdn.bootcdn.net/ajax/libs/signature_pad/4.0.5/signature_pad.min.js
- https://cdn.bootcdn.net/ajax/libs/signature_pad/4.0.5/signature_pad.umd.js
- https://cdn.bootcdn.net/ajax/libs/signature_pad/4.0.5/signature_pad.umd.min.js