bug#52973: Adding a few context-menu-mode commands

[Eli Zaretskii]

> From: Juri Linkov <juri@linkov.net>
> Cc: philipk@posteo.net,  52973@debbugs.gnu.org
> Date: Tue, 04 Jan 2022 19:46:31 +0200
> 
> > But in any case, we need to do this soon, because adding functions
> > that are not used unless the user plays with hooks is not clean,
> > definitely not for a feature such as this one, because it's supposed
> > to be very easy, ideally seamless, to activate.  Otherwise it would be
> > against the raisons d'être of the feature.
> 
> The main customization point is
> 
>   'M-x customize-variable RET context-menu-functions'
> 
> that will provide more choices with the help of
> 'custom-add-repeat-choice'.

I think once the user turns on context-menu-mode, all the modes that
defined their context menus should automatically activate them.  There
should be no need for any user customizations except turning on this
mode.