Prep for v4.2.0 release

- Move 4.1 docs to 4.2
- Update versions everywhere to 4.1.3 with release script
- Manually bump the shorthand version in package.json
- Add 4.2 to the versions docs page
- Update some redirects
- Fix tests asset URLs
- Bump Nuget and more

site/docs/4.2/utilities/visibility.md

@@ -0,0 +1,33 @@
+---
+layout: docs
+title: Visibility
+description: Control the visibility, without modifying the display, of elements with visibility utilities.
+group: utilities
+---
+
+Set the `visibility` of elements with our visibility utilities. These utility classes do not modify the `display` value at all and do not affect layout – `.invisible` elements still take up space in the page. Content will be hidden both visually and for assistive technology/screen reader users.
+
+Apply `.visible` or `.invisible` as needed.
+
+{% highlight html %}
+<div class="visible">...</div>
+<div class="invisible">...</div>
+{% endhighlight %}
+
+{% highlight scss %}
+// Class
+.visible {
+  visibility: visible;
+}
+.invisible {
+  visibility: hidden;
+}
+
+// Usage as a mixin
+.element {
+  @include invisible(visible);
+}
+.element {
+  @include invisible(hidden);
+}
+{% endhighlight %}