* Easier to browse plugin README.md

* Splits are inverted

* $SPLIT clarification and default values for $SPLIT and $TERMINAL

* Unified preview-tui and preview-kitty

* Remove preview-kitty

* No need to set $TERMINAL

* fix undeclared variable

* Integrated support for scope.sh

* Review fixes

* allow_remote_control must be enabled on kitty

* Documentation, kitty splits and images fallback

* fix restoring kitty layout

In the dash shell, when `exec < fifo` is interrupted by SIGCHLD, it exits.
So we replace it with `cat fifo |`.

Issue discussed in #614

Fixed typo in preview-kitty.

Thanks @Kabouik!

* Added GPG encrypt and decrypt plugins

* Made description more descriptive

Co-authored-by: Todd Yamakawa <todd.yamakawa@arm.com>

* preview-tui: simplify, add generic fifo_pager()

I've commented new filetype checks for now, as we need to discuss which ones
should be included by default, keeping in mind that this is supposed to be a
minimal, adaptable plugin.

* preview-tui: preview with man, tar, unzip by default

We leave it undefined on Solaris/Illumos because no such options exist,
so only use it if we have it.