[Keymap Removal] Restore splitkb 'debug' keymaps (#22700)

keyboards/splitkb/kyria/keymaps/debug/readme.md

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+# Kyria's Debug Keymap
+
+To make debugging your build as easy as possible, we have provided a special debugging keymap. It is not intended to actually type on, it is just here to make sure that your hardware is working correctly.
+
+## Keys
+
+![Keys](https://i.imgur.com/pmPBYlkh.png)
+
+The left side uses lowercase letters, the right side uses uppercase ones.
+
+## Encoders
+
+Encoders output a number of 0 or 1, depending on the installed position.
+These correspond to the index used for custom encoder code.
+
+The number is followed by either a `+` or a `-`, depending on the direction turned.
+
+## LEDs
+
+Both underglow and per-key RGB should be fading between red and off.
+
+## OLEDs
+
+Both the primary and secondary side should be filled with characters.