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

[Juri Linkov]

>>> So it sounds to me like shell-script-mode (and derivatives and other
>>> shell-ish modes) should have the `man' bits of the context menu enabled
>>> by default?
>>
>> Nope.  This `man' menu item might be useful everywhere, for example,
>> in this Gnus Article buffer, to look up the command cited above.
>
> It might be, and I think it's fine to let people customise that, if they
> want it.

Agreed, everyone can customize the contents of their context menus.
But Eli wants to reject new functions only because they are not added
to the menu by default.

> But it seems to me like that context menu should work by default in
> shell-script-modeish buffers -- I think pretty much everybody would like
> to have it there.

Actually, the context menu already works by default in all shell related modes.
The problem is that adding the man-menu item by default will load man.el
in every shell-script buffer.