Add graphical zone editor and update documentation

- Implemented visual zone editor (Super+Shift+E)
- Draw zones with mouse click-and-drag
- Ctrl+S to save, Ctrl+C to cancel, Delete to remove last zone
- Updated README with zone editor documentation
- Added CSS styles for editor interface
- Custom layouts are now created without code editing

stylesheet.css

@@ -20,3 +20,28 @@
     font-weight: bold;
     text-shadow: 2px 2px 4px rgba(0, 0, 0, 0.8);
 }
+
+.gridsnap-editor-overlay {
+    background-color: rgba(0, 0, 0, 0.5);
+}
+
+.gridsnap-editor-zone {
+    border: 3px solid rgba(100, 255, 100, 0.9);
+    background-color: rgba(100, 255, 100, 0.3);
+    border-radius: 4px;
+}
+
+.gridsnap-editor-instructions {
+    color: white;
+    font-size: 18px;
+    background-color: rgba(0, 0, 0, 0.8);
+    padding: 15px;
+    border-radius: 8px;
+}
+
+.gridsnap-editor-zone-label {
+    color: white;
+    font-size: 24px;
+    font-weight: bold;
+    text-shadow: 2px 2px 4px rgba(0, 0, 0, 0.8);
+}