Suggest -o display_link_number=1

Apparently this w3m option is not very well known, to the point where
people are advised to switch to lynx.

docs/source/faq.rst

@@ -10,6 +10,10 @@ Try `w3m <http://w3m.sourceforge.net/>`_ and put the following into your
 
    text/html;  w3m -dump -o document_charset=%{charset} '%s'; nametemplate=%s.html; copiousoutput
 
+On more recent versions of w3m, links can be parsed and appended with reference numbers::
+
+   text/html;  w3m -dump -o document_charset=%{charset} -o display_link_number=1 '%s'; nametemplate=%s.html; copiousoutput
+
 Most `text based browsers <http://en.wikipedia.org/wiki/Text-based_web_browser>`_ have
 a dump mode that can be used here.
 

docs/source/installation.rst

@@ -11,6 +11,10 @@ On a recent Debian (-derived) systems for instance, just do `sudo apt install al
    (copiousoutput) set up for `text/html` in your :file:`~/.mailcap`::
 
      text/html;  w3m -dump -o document_charset=%{charset} '%s'; nametemplate=%s.html; copiousoutput
+
+   On more recent versions of w3m, links can be parsed and appended with reference numbers::
+
+     text/html;  w3m -dump -o document_charset=%{charset} -o display_link_number=1 '%s'; nametemplate=%s.html; copiousoutput
    
    See the manpage :manpage:`mailcap(5)` or :rfc:`1524` for more details on your mailcap setup.