Key-value pairs trigger example

- Include example demonstrating
  a rule to use key-value based
  internal trigger resulting
  into an action

Signed-off-by: NitinNahal <nitin.nahal14@gmail.com>

Author: NitinNahal

docs/source/sensors.rst

@@ -31,6 +31,25 @@ A list of available triggers for each resource is included below:
 
 .. _ref-sensors-authoring-a-sensor:
 
+An example rule to use ``core.st2.key_value_pair.*`` triggers is included below:
+.. code-block:: yaml
+
+    trigger:
+    type: "core.st2.key_value_pair.create"
+
+    criteria:
+        trigger.object.name:
+            type: "eq"
+            pattern : "x"
+
+    action:
+        ref: "core.local"
+        parameters:
+            cmd: "echo {{ trigger.object }}"
+
+Above rule will execute whenever a new key-value pair with name ``x`` is created in the
+datastore. The action will print the details of the created key-value pair.
+
 Creating a Sensor
 -----------------