refactor(build): modularize JS code

- replace gulp with rollup
- remove JS output from repo

_javascript/modules/components/img-extra.js

@@ -0,0 +1,27 @@
+/**
+ * Set up image stuff
+ */
+
+export function imgExtra() {
+  if ($('#core-wrapper img[data-src]') <= 0) {
+    return;
+  }
+
+  /* See: <https://github.com/dimsemenov/Magnific-Popup> */
+  $('.popup').magnificPopup({
+    type: 'image',
+    closeOnContentClick: true,
+    showCloseBtn: false,
+    zoom: {
+      enabled: true,
+      duration: 300,
+      easing: 'ease-in-out'
+    }
+  });
+
+  /* Stop shimmer when image loaded */
+  document.addEventListener('lazyloaded', function (e) {
+    const $img = $(e.target);
+    $img.parent().removeClass('shimmer');
+  });
+}