Add README.md and screenshot

Maildir.py

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 #
-# Copyright (C) 2022, Jaidyn Levesque <jadedctrl@posteo.at>
+# Copyright (C) 2023, Jaidyn Levesque <jadedctrl@posteo.at>
 #
 # This program is free software: you can redistribute it and/or
 # modify it under the terms of the GNU General Public License as

README.md

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+# Nautilus-Maildir / Caja-Maildir / Nemo-Maildir
+
+A simple plugin for Caja/Nemo/Nautilus that adds email metadata as columns to your file-manager. This makes maildir folders more friendly-to-browse.
+
+![A screenshot of the file-manager Caja displaying several email files from the emacs-devel mailing list three separate columns: From; Subject; and Sent.](res/list_screenshot.png)
+
+## Installation
+To make the version of the script appropriate for your file-manager, you can just replace 'Caja'/'caja' in Maildir.py with 'Nemo'/'nemo', etc. This is thanks to the scripting interfaces between Caja, Nemo, and Nautilus being more-or-less identical. Alternatively…
+
+`$ make caja; make nemo; make nautilus`
+
+Then you can copy the resultant script into `~/.local/share/[caja|nemo|nautilus]-python/extensions/` or `/usr/share/[caja|nemo|nautilus]-python/extensions/`. Or…
+
+`$ make install-caja; make install-nemo; make install-nautilus`
+
+
+## Meta
+Author is jadedctrl, and the license is the GNU GPLv3+ (in COPYING.txt).
+
+https://notabug.org/jadedctrl/nautilus-maildir  
+https://github.com/jadedctrl/nautilus-maildir