✨ feat: add 2 interactive image shortcodes

- `image_hover` changes image on mouse hover.

- `image_toggler` swaps image on click.

sass/parts/_image-toggler.scss

@@ -0,0 +1,20 @@
+.image-toggled {
+    visibility: hidden;
+    position: absolute;
+    top: 0;
+    left: 0;
+}
+
+.image-toggler-toggle {
+    display: none;
+}
+
+.image-toggler-toggle:checked ~ .image-label .image-toggled {
+    visibility: visible;
+    position: static;
+}
+
+.image-toggler-toggle:checked ~ .image-label .image-default {
+    visibility: hidden;
+    position: absolute;
+}