Add readme and layout graph

readme.md

@@ -0,0 +1,36 @@
+# zmk-config
+
+This is my personal [ZMK firmware](https://github.com/zmkfirmware/zmk/) configuration. 
+It is ported from my QMK configuration, which in turn is heavily inspired by Manna Harbour's
+[Miryoku layout](https://github.com/manna-harbour/miryoku).
+
+## Key features
+
+- simple macro-implementation of combos and keymap to fit different physical keyboards
+- home-row mods on base layer, sticky mods on `Nav` and `Num` layers
+- most symbols can be accessed from the base layer via combos
+- sticky shift on right thumb, double-tap activates caps-word
+- backspace morphs into delete when shifted
+- unicode layer with Greek letters for mathematical typesetting (not yet ported to ZMK)
+
+## Keymap layout
+
+![](keymap.png)
+
+## Thoughts on combo layout
+
+The combo layout is guided by two goals: (1) put all combos in easy-to-access locations,
+and (2) make them easy to remember. Specifically:
+
+- the top vertical-combo row is almost equivalent to the symbols on standard number rows,
+  making them easy to remember
+- the bottom vertical-combo row is set up symmetrically to facilitate memorization
+  (subscript `_` aligns with superscript `^`; `-` aligns with `+`; division `/` aligns 
+  with multiplication `*`; logical-or aligns with logical-and; back-slash aligns 
+  horizontally with forward-slash)
+- parenthesis, brackets, braces and punctuation are on the right-hand side for easy
+  usage when typing numbers
+- a numlock shortcut (on `W+P`) is on the left-hand side for one-handed number-mode
+- shortcuts for cut (on `X+D`), copy and paste are on the left-hand side for one-handed
+  usage when using the mouse
+