Incorrect mail link in documentation

[Dave Atkinson]

Dear Lilypond Devs,

I'm reading the "Lilypond - Extending" docs for 2.19.84 and I went to 
report a possible bug. At the bottom of every page there is a bug 
reporting link in this sentence:

We welcome your aid; please help us <http://lilypond.org/help-us.html> 
by reporting errors to our bug list 
<mailto:https://lists.gnu.org/mailman/listinfo/bug-lilypond>.

Examining the link in "bug list" shows it points to 
mailto:https://lists.gnu.org/mailman/listinfo/bug-lilypond

When clicked on this brings up a mailer window with the address 
pre-filled to a webpage, not an email address. Surely it should either be

mailto:bug-lilypond@gnu.org

or just a link

https://lists.gnu.org/mailman/listinfo/bug-lilypond

This seems to be present in 2.21.1 as well.

Best regards,

Dave