[Keyboard] move @Biacco42 's keebs into /biacco42 (#16080)

keyboards/biacco42/ergo42/keymaps/koba/readme.md

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+# Keymap for Ergo42
+
+## About
+
+This keymap is for Ergo42.
+
+- JIS layout.
+- Independent Windows layout/MacOS layout layers.
+- Bottom row keys are arranged like a standard keyboard.
+- Arrow keys are designed in the inverted-T.
+
+## Layout
+
+![keyboard-layout](https://user-images.githubusercontent.com/1042121/52666273-32a45e00-2f51-11e9-9e15-c231155f3bed.png)
+
+## Windows mode/MacOS mode
+
+|mode        |key         |
+|------------|------------|
+|Windows mode|Function + g|
+|MacOS mode  |Function + b|
+
+When switching mode, the following keys switches.
+
+|Windows        |MacOS       |
+|---------------|------------|
+|Alt            |Command(GUI)|
+|Windows(GUI)   |Option(Alt) |
+|Menu(App)      |Command(GUI)|
+|Muhenkan       |Eisu        |
+|Henkan         |Kana        |
+|Hankaku/Zenkaku|Caps        |
+
+## Layers
+
+|No.|Name    |Description                |
+|---|--------|---------------------------|
+| 4 |Function|Mode switch, Media         |
+| 3 |Raise   |Number, Function           |
+| 2 |Lower   |Symbol, Home/End, PgUp/PgDn|
+| 1 |MacOS   |MacOS layout               |
+| 0 |Windows |Windows layout             |
+
+When power is turn on, No.0 Windows layer becomes enabled.
+
+## Windows/MacOS layers
+
+Standard layers for Windows mode/MacOS mode.
+
+## Raise/Lower layers
+
+Layer enabled during pressing Raise or Lower key.
+
+## Function layer
+
+Layer enabled during pressing Function key.
+