Proposal to add Popper to ELPA

[Karthik Chikmagalur <karthikchikmagalur@gmail.com>]

I would like to add my package Popper to GNU ELPA.

URL: https://github.com/karthink/popper

What is Popper?

Short for "Popup Buffer", it's a global minor mode that designates
buffers as "popups", which means their display can be toggled with a
single key-press.  This is useful for quickly displaying and dismissing
"auxiliary" buffers like shells, compilation, help/man, grep buffers
etc.  If you have used the guake/yakuake pull-down terminals on GNOME or
KDE, the experience should be similar.

- You can designate a buffer as a "popup" manually or automatically
  ahead of time via name/major-mode or any predicate of your choosing.

- You can cycle through your popups with one key.

- You can group your popups by any predicate: for example, by project so
  that you only see auxiliary buffers relevant to your current project.

There are other features, and a few video demos at the link.

There are a few other packages that do this kind of thing, but they are
one or more of:

- Unmaintained (Popwin).

- Too limited in scope.  For example, the shellpop and vterm-toggle
packages allows this kind of behavior but only for shells.  Popper is
generic.

- Too rigid/overarching in their display behavior.  In contrast, Popper
does not try to control how popups are displayed: your
display-buffer-alist rules are respected, so that it composes well with
your other packages or customizations involving buffer display.

This package is now 4+ years old and (I think) in a stable state.  It
has been installed 16,000+ times.

Copyright assignment: I have signed the FSF copyright assignment papers.
Popper has several other contributors, but each of their contributions
is limited to 1-2 lines, usually fixing a linting issue or typo.

Please let me know if need more information or have any concerns.

Karthik