[DOCS] Create a community section in the documentation. (#671)

* [DOCS] Create a community section in the doc.

This section is meant to host the non-official documentation
produced by the community.

Fixes #582.

* Update index.md

docs/community/index.md

@@ -0,0 +1,13 @@
+---
+layout: default
+title: Community
+nav_order: 8
+has_children: true
+---
+
+# Community documentation
+
+This section is meant to advertise and organize documentation produced
+by the community. This documentation is considered non-official and we
+will not guarantee that this documentation is up-to-date. If you think
+some of it should be considered official, please file an issue on Github.

docs/community/two-factor-basic-auth.md

@@ -0,0 +1,11 @@
+---
+layout: default
+title: 2FA through basic auth
+parent: Community
+nav_order: 1
+---
+
+The following documentation shows how to integrate one-time password
+second factor through basic auth.
+
+Check the documentation available at https://github.com/ViRb3/authelia-basic-auth-2fa.