Markdown footnote anchors append to root url

[HerrGertrud]

Proposal description supports markdown footnotes but the resulting anchors append to the snapshot root url instead of the open proposal which breaks their funcitonality and issues a warning "leaving page".

Example reproducer:

## Example
Text block with footnote[^1] continuing to footnote[^2].

[^1]: This is where the link should route for footnote 1
[^2]: This is where the link should route for footnote 2

--- 

### Second chapter
Lorem ipsum
- dolor
- sit
- amet

[mktcode]

I think the other problem is the Vue router using anchors for routes instead of the browser's history API.

Thoughts:

• Extend the parser to generate custom (js based) scroll links.
• Collapsed long proposal texts need to be expaneded when clicking on a footnote.
• Use history API instead (which requires redirecting old links, which can only be done in the client)
• Disable the syntax and make it clear that it is not supported or at least doesn't support linking to the footnotes.