Add 404 page (#4029)

* add 404 page

Signed-off-by: Heather Halter <hdhalter@amazon.com>

* added link

Signed-off-by: Heather Halter <hdhalter@amazon.com>

* update text on 404 page

Signed-off-by: Heather Halter <hdhalter@amazon.com>

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Signed-off-by: Heather Halter <hdhalter@amazon.com>

404.md

@@ -1,3 +1,17 @@
 ---
 permalink: /404.html
+layout: error
+errormessage: 🙅‍♀️ 404
+body_class: homepage
+errorhuman: "OpenSearch can't find that page." 
 ---
+
+Sorry about that. Perhaps we moved something around, or you mistyped the URL? 
+
+
+Head to the [OpenSearch Documentation home page](https://opensearch.org/docs/latest/) or try our [community forum](https://forum.opensearch.org/).
+
+
+
+
+

index.md

@@ -3,7 +3,6 @@ layout: default
 title: OpenSearch documentation
 nav_order: 1
 has_children: true
-redirect_from: /404.html
 permalink: /
 ---