Move more modules from flavours/glitch/utils to flavours/glitch

app/javascript/flavours/glitch/load_keyboard_extensions.js

@@ -0,0 +1,16 @@
+// On KaiOS, we may not be able to use a mouse cursor or navigate using Tab-based focus, so we install
+// special left/right focus navigation keyboard listeners, at least on public pages (i.e. so folks
+// can at least log in using KaiOS devices).
+
+function importArrowKeyNavigation() {
+  return import(/* webpackChunkName: "arrow-key-navigation" */ 'arrow-key-navigation');
+}
+
+export default function loadKeyboardExtensions() {
+  if (/KAIOS/.test(navigator.userAgent)) {
+    return importArrowKeyNavigation().then(arrowKeyNav => {
+      arrowKeyNav.register();
+    });
+  }
+  return Promise.resolve();
+}