add missing file for about page

data/content_overview.json

+{
+  "property_dict": {},
+  "children": [
+    {
+      "type": "p",
+      "direct": {"className": "translate"},
+      "attributes": {"data-i18n": "global_dict.find_out_more_details"},
+      "logic": {"text": "For additional information, please refer to the following sections:"}
+    },
+    {
+      "generate": "widget",
+      "type": "listview",
+      "class_list": null,
+      "theme": "slapos-black",
+      "form": null,
+      "property_dict": {
+        "inset": true
+      },
+      "children": [
+        {"type": "item", "href": "http://community.slapos.org/wiki", "external": true, "left": {"icon":"book"}, "center": {"text": [{"type": "h1", "text": "Documentation", "text_i18n":"global_dict.documentation"}]}},
+        {"type": "item", "href": "http://community.slapos.org/download", "external": true, "left": {"icon":"download"}, "center": {"text": [{"type": "h1", "text": "Download", "text_i18n":"global_dict.download"}]}},
+        {"type": "item", "href": "http://community.slapos.org/forum", "external": true, "left": {"icon":"comments-alt"}, "center": {"text": [{"type": "h1", "text": "Forum", "text_i18n":"global_dict.forum"}]}},
+        {"type": "item", "href": "http://community.slapos.org/blog", "external": true, "left": {"icon":"rss-sign"}, "center": {"text": [{"type": "h1", "text": "Blog", "text_i18n":"global_dict.blog"}]}},
+        {"type": "item", "href": "http://www.vifib.com/vifib-Pricing", "external": true, "left": {"icon":"dollar"}, "center": {"text": [{"type": "h1", "text": "Pricing", "text_i18n":"global_dict.pricing"}]}}
+      ]
+    }
+  ]
+}
\ No newline at end of file