user-defined html in navigation header/footer?

[Karl Berry]

Hi Gavin and all - I suggest it would be useful to support a
user-defined navigation "button" that would appear next to [Contents]
xand [Index]. (If it's already possible, please let me know. I couldn't
find it in the doc or souces.)

Just one user variable seems like it would suffice, say
USER_NAVIGATION_HTML

It would be inserted wherever the other buttons are.

The thing I want to do (and that would seemingly be nice to have for
just about every package), is a link to the package home page. As in,

-c USER_NAVIGATION_HTML="[<a href="https://gnu.org/software/texinfo/";>Home</a>]"

But I can imagine people wanting to have more buttons, or something else
entirely, so just as well to make it a generic feature.

Looking at Convert/HTML.pm, I admit it's not obvious to me where/how to
implement this, but I hope it would not be hard.

Wdyt? --thanks, karl.