Expand README with SynthX keyboard layout details

Added detailed description of SynthX keyboard layout, including features and design philosophy.

Author: barnacker

README.md

@@ -1,2 +1,37 @@
-zmk-config for charybdis (4x6)
+# SynthX Keyboard Layout
+A custom keyboard layout optimized for split ortholinear keyboards, designed for comfortable and efficient typing on boards like the Corne (Chocofi).
+
+## Layout Overview
+
+SynthX is a custom alpha layout that prioritizes home row comfort and logical symbol placement for programming and general typing.
+
+### Alpha Keys
+
+```
+F B K L J     = W ' / .
+S N T H V     G C A E I
+X P D M Q     Z Y O U ,
+```
+
+<img width="1288" height="600" alt="image" src="https://github.com/user-attachments/assets/8fb45a9d-1e26-4636-ad5b-2e33318c1bf4" />
+
+### Key Features
+
+- **Home Row Mods**: GACS on left (GUI, Alt, Ctrl, Shift), SCAG on right
+- **Common Punctuation**: Strategic placement of quotes, slashes, and periods on the right side
+- **Comfortable Rolls**: Optimized letter combinations for English
+- **Split-Friendly**: Designed specifically for column-stagger split keyboards
+
+## Character Mappings
+
 <img width="788" height="2016" alt="my_keymap" src="https://github.com/user-attachments/assets/bc24690c-d536-4099-8741-f4dd4209398f" />
+
+## Design Philosophy
+
+SynthX was designed with the following principles:
+
+1. **Home Row Optimization**: Most frequent letters placed on the home row
+2. **Hand Alternation**: Balanced workload between hands
+3. **Common Bigrams**: Frequently typed letter pairs placed for comfortable rolls
+4. **Symbol Access**: Programming symbols easily accessible without excessive stretching
+5. **Split Ergonomics**: Designed for split keyboards with home row mods