Add urlmap.js to doc/Makefile.am
Add urlmap.js to doc/Makefile.am

Can't wait to get rid of autotools.

Part-of: <https://gitlab.gnome.org/GNOME/librsvg/-/merge_requests/678>

GNOME/librsvg,GNOME/librsvg,GNOME/librsvg,GNOME/librsvg