Add deprecation warning to release-1.4 (#4756)

* Add Version Selector to v1.4

* upgrade to newer header

* change include_cached to include

* move head.html to correct location

* remove seo

* add footer-scripts.html

* turn on global nav

* fix docs nav link

* Add deprecation warning to release-1.4

* remove warning from index.html

* add newlines

_config.yml

@@ -40,6 +40,9 @@ defaults:
           githubbranch: "v1.4.12"
           docsbranch: "release-1.4"
           url: https://v1-4.docs.kubernetes.io/docs/
+      deprecated: true
+      currentUrl: https://kubernetes.io/docs/home/
+      nextUrl: http://kubernetes-io-vnext-staging.netlify.com/
   -
     scope:
       path: "docs"