Feature request: graph view among notes

Hi, dear Hackmd team

Hackmd is really a super nice tool for online notetaking. I am just wondering if graph view of notes can be considered for future features. More details of this feature has been implemented in this app -- [Obsidian](https://obsidian.md/). I know it won't be easy for adding this wonderful feature, but if this is added into hackmd, the whole system will be fantastic :)