feat(shields): add physical layouts and update keymap for Jian

Add physical layouts and update the keymap for King of Hedgehogs' Jian.
Layouts are added for all three possible transforms:
- Full (with additional pinky key)
- 6 column (Corne)
- 5 column (Minidox)

The layouts are added to be re-usable for the Jiran and other custom boards/shields.

Keymap update includes, small guide clarifications, output selection,
tri-layer and &studio_unlock.

app/dts/layouts/kgoh/jian/position_map.dtsi

@@ -0,0 +1,7 @@
+/ {
+    layouts_kgoh_jian_position_map: layouts_kgoh_jian_position_map {
+        compatible = "zmk,physical-layout-position-map";
+
+        complete;
+    };
+};