Add Rancher extension doc (#79)

Signed-off-by: RokibulHasan7 <mdrokibulhasan@appscode.com>

Author: RokibulHasan7

src/_home-integrations.md

@@ -0,0 +1,10 @@
+---
+menu:
+  home_menu:
+    identifier: home-integrations
+    name: Integrations
+    description: Manage licenses for AppsCode's products
+    link: /en/guides/integrations/rancher-extension.html
+    icon: https://img.icons8.com/?size=100&id=80695&format=png&color=000000
+    weight: 20
+---

src/en/guides/integrations/_index.md

@@ -0,0 +1,13 @@
+---
+layout: 'guide'
+menu:
+  docs_menu:
+    identifier: integrations
+    name: Integrations
+    description: Integrate ACE into your Kubernetes platform
+    icon: https://img.icons8.com/?size=100&id=80695&format=png&color=000000
+    popular: true
+    weight: 40
+menu_name: docs_menu
+section_menu: guides
+---