feat: add mobile virtual touch controls

- document.js: add is_touch detection and virtual button CSS
- input.js: create virtual D-pad + action buttons + touch drag camera
- main.js: skip Pointer Lock on touch devices

source/main.js

@@ -124,8 +124,10 @@ game_load = async () => {
 
 	f.onclick = () => g.requestFullscreen();
 	g.onclick = () => {
-		g.onclick = () => c.requestPointerLock();
-		g.onclick();
+		if (!is_touch) {
+			g.onclick = () => c.requestPointerLock();
+			g.onclick();
+		}
 		
 		audio_init();