Missing link for reporting issues in manuals page

[dforsi]

The page at https://dm3mat.darc.de/qdmr/manual/re02.html doesn't render the web address for reporting issues.

This is the text visible at the end of the page:

If you stumble across one of them, consider opening an issue at <xlink></xlink>.

And this is a screenshot:

[hmatuschek]

Fixed that in master, will be updated with the next release.