add fetchp example with post data

docs/variables/fetchp.rst

@@ -8,18 +8,19 @@ Resolves the response from the url using a POST request. Similar to :doc:`$(fetc
     To avoid hitting any rate limits against remote APIs, all responses are cached for 5 seconds.
 
 Usage:
-    $(fetchp ``<url>`` ``[data]``)
+    $(fetchp ``<url>`` ``[data]`` ``[path]``)
 
 Arguments:
     * ``url`` **<required>** - The url to send the request to
     * ``data`` **[optional]** - The data string to send to the url
+    * ``path`` **[optional]** - The path to the property in the response (JSON only)
 
 Example Command:
-    **name**: !kanye
+    **name**: !dadjoke
 
-    **response**: $(fetchp https://api.kanye.rest/?format=text) - Kanye
+    **response**: $(fetchp https://icanhazdadjoke.com/graphql query=$(urlencode query { joke {id joke permalink } }) data.joke.joke)
 
     **output**::
 
-        user:     !kanye
-        botisimo: I'm a creative genius - Kanye
+        user:     !dadjoke
+        botisimo: Why are skeletons so calm? Because nothing gets under their skin.