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/examples/checkout/form-validation.css

@@ -0,0 +1,5 @@
+.container {
+  max-width: 960px;
+}
+
+.lh-condensed { line-height: 1.25; }