ADPenrose Akemipad Layout Addition (#20957)

* add matrix_diagram.md

* info.json: apply friendly formatting

* add LAYOUT_numpad with reference keymap

keyboards/adpenrose/akemipad/keymaps/default_numpad/readme.md

@@ -0,0 +1,12 @@
+# The default_numpad keymap for the AkemiPad
+
+
+## Features
+- Audio Click and Music Mode capabilities.
+- RGB Matrix Lighting (cycles left-right and up-down).
+- Encoder Map feature.
+
+### Disclaimer
+The AkemiPad has multiple layout options (each one with its own LED positions), but this keymap does not take that into consideration.
+If you want to select an specific layout (and see how the LEDs turn on and off accordingly), you
+should use the [via keymap](../via).