Add new keymap for Preonic rev3 (#19706)

keyboards/preonic/keymaps/guillermoap/readme.md

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+# Preonic Double Spacebar HHKB layout mainly for programming
+This layout is highly curated to my needs and what I like. I mainly use it for programming in macOS, but also gaming in Windows.
+
+The main concept behind every key position is to be able to maximize how many things I can do without lifting my hands from the home row.
+## Layers
+### Base
+- Ctrl/Cmd is on the Caps Lock place (HHKB like)
+- Enter and Space are in the double space bar
+- Normal arrows position (not vim-like)
+- Left Shift on hold - Caps Lock Toggle on tap
+- Vertical scroll on encoder
+### Gaming
+- Switched Enter and Space to reach more easily when gaming
+- Left Shift doesn't have Caps Lock toggle
+- ` is in Ctrl space, mainly used for Push To Talk in games
+### Lower
+- Main programming symbols with right hand
+- Media controls with left hand
+- Full F1..F12 Function keys on number row
+- Ctrl + C | Ctrl + Z Macros to avoid having to constantly press encoder
+- Ctrl + Tab | Ctrl + Shift + Tab on encoder
+### Raise
+- Arrow keys on JKLI
+- Home End PgUp PgDown on M,.Up
+- Numbers on asdfgqwert
+- Del on BackSpace
+- Horizontal scroll on encoder
+### Config
+- Swap Ctrl and GUI on H so I have Cmd next to KC_A when on MacOS
+- Unswap Ctrl and GUI on G so I have Ctrl next to KC_A when on Windows
+- J switches to BASE layer
+- K switches to GAMING layer
+- Default Config for Preonic