mindmap fix

I'm using the [markmap](https://github.com/markmap/markmap) to build a mindmap live on mindmap.openprivacytech.org

>  the initial content is in [mindmap.md](https://github.com/openprivacytech/mindmap/blob/main/mindmap.md)

references
- https://github.com/markmap/markmap
- https://markmap.js.org/docs/markmap

 run it on your local server and submit a pull request.