don't block regular keyboard shortcuts

glsl/raymarching.js

@@ -237,7 +237,7 @@ void main() {
    });
    
    window.addEventListener('keydown', function(ev) {
      if (document.activeElement != document.body) {
      if (document.activeElement != document.body || ev.ctrlKey || ev.altKey) {
        return;
      }