Write up the README

[KevinBockelandt]

Talk about:

• What Zettelkasten is about. Give a few links
• The mapping for hotkeys
• The roadmap
• Other tools that implement the zettelkasten method
• How to install
• How to use (directory setup, backup of notes, etc.)
• Meaning of the name

[KevinBockelandt]

Basic version done with 060cc8f477ef2aa61149bb102cda4bfc2a512735

Remains to do:

• What Zettelkasten is about. Give a few links
• Other tools that implement the Zettelkasten method
• Meaning of the name

[KevinBockelandt]

Done with https://github.com/KevinBockelandt/notoire/commit/c018aade6ddf10e61ad2016cff09a8694d66aac9