Fix typo error and update index

Signed-off-by: Wen Cheng Ma <wenchma@cn.ibm.com>

docs/extend/index.md

@@ -18,4 +18,5 @@ Currently, you can extend Docker by adding a plugin. This section contains the f
 * [Understand Docker plugins](plugins.md)
 * [Write a volume plugin](plugins_volume.md)
 * [Write a network plugin](plugins_network.md)
+* [Write an authorization plugin](authorization.md)
 * [Docker plugin API](plugin_api.md)

docs/extend/plugins_network.md

@@ -51,7 +51,7 @@ documented as part of libnetwork:
 
 # Related Information
 
-To interact with the Docker maintainers and other interested users, se the IRC channel `#docker-network`.
+To interact with the Docker maintainers and other interested users, see the IRC channel `#docker-network`.
 
 -  [Docker networks feature overview](../userguide/networking/index.md)
 -  The [LibNetwork](https://github.com/docker/libnetwork) project