Added README.

README.md

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+A Kanban editor for your TODO.md Markdown file, in a single `index.html` file.
+
+## Format
+
+```
+# Project name
+
+## Column name
+
+- [ ] Task number one.
+- [ ] Some other task.
+
+## Another column
+
+- [ ] Yet another task.
+```
+
+## Self host
+
+Copy `index.html` and `kbtd` up to your server.
+
+Then visit the page and download `kbtd` and put it on your path.