Describe how to create new library and share it

docs/userguide/lib/cmd_register.rst

@@ -0,0 +1,26 @@
+.. _cmd_lib_register:
+
+platformio lib register
+=======================
+
+.. contents::
+
+Usage
+-----
+
+.. code-block:: bash
+
+    platformio lib regiter [HTTP_URL_TO_LIBRARY.JSON]
+
+
+Description
+-----------
+
+Register new library and allow others to install it.
+
+Examples
+--------
+
+.. code-block:: bash
+
+    $ platformio lib register http://my.example.com/library.json

docs/userguide/lib/index.rst

@@ -16,6 +16,7 @@ To print all available commands and options use:
 
     cmd_install
     cmd_list
+    cmd_register
     cmd_search
     cmd_show
     cmd_uninstall