bug#53981: 28.0.91; shortdoc: Add support for outline-minor-mode

[Juri Linkov]

>> - how commonly is this library used (i.e. is it worth carrying the
>>   N autoloads in every Emacs session, compared to having to write
>>   `require` in a handful of files).
>
> The answer to this one is that we currently have just 2 packages that
> require this library.

I counted more:

- lisp/emacs-lisp/multisession.el
- lisp/emacs-lisp/shortdoc.el
- lisp/emacs-lisp/vtable.el
- lisp/gnus/gnus-util.el
- lisp/help.el
- lisp/image/image-crop.el
- lisp/international/mule-cmds.el
- lisp/net/eww.el
- lisp/net/shr.el
- lisp/net/tramp-crypt.el
- lisp/progmodes/compile.el
- lisp/textmodes/enriched.el
- lisp/textmodes/string-edit.el

All they use text-property-search-forward and text-property-search-backward
as entry points.