Add better 404 page (#212)

Signed-off-by: Aleksandr Radchenko <dacetascien@gmail.com>

Author: dacetascien

content/documentation/404.md

@@ -1,7 +1,14 @@
 ---
-title: "Page Not Found"
+title: "Page not found"
+custom_class: "section"
 noindex: true
 hidden: true
+searchable: false
+sitemap_include: false
+toc: false
+breadcrumbs: false
+feedback: false
+sidebar: false
 ---
 
-The requested page was not found.
+- [Deckhouse Development Platform Documentation](/products/development-platform/documentation/)

content/documentation/404.ru.md

@@ -1,7 +1,14 @@
 ---
 title: "Страница не найдена"
+custom_class: "section"
 noindex: true
 hidden: true
+searchable: false
+sitemap_include: false
+toc: false
+breadcrumbs: false
+feedback: false
+sidebar: false
 ---
 
-Запрошенная страница не найдена.
+- [Документация Deckhouse Development Platform](/products/development-platform/documentation/)