bug#50364: 27.2; EDT mode Xmodmap related documentation needs updating

[Eli Zaretskii]

> Date: Tue, 19 Oct 2021 14:42:09 +0000 (UTC)
> From: Hin-Tak Leung <htl10@users.sourceforge.net>
> Cc: 50364@debbugs.gnu.org, ca22@cam.ac.uk
> 
> On Saturday, 4 September 2021, 07:19:39 BST, Eli Zaretskii <eliz@gnu.org> 
> wrote:
> 
> > Thanks.  Would you like to write some text that explains how to
> > achieve this on modern platforms?  We could then update or augment
> > what the manual says as appropriate.
> 
> I should say that I intend to come back to this, and submit a patch/diff to 
> the documentation when I find the
> time to do so. Hopefully before Christmas... 

Thanks in advance.