Add example for human readable uptime sensor (#923)

* Add example for human readable uptime sensor

* Fix lint

* simpler return

components/sensor/uptime.rst

@@ -23,6 +23,45 @@ Configuration variables:
 - **id** (*Optional*, :ref:`config-id`): Set the ID of this sensor for use in lambdas.
 - All other options from :ref:`Sensor <config-sensor>`.
 
+Human readable sensor
+---------------------
+
+The sensor reports uptime in seconds which is good for automations
+but is hard to read for humans, this example creates a text sensor
+with human readable output.
+
+.. code-block:: yaml
+
+    # Example configuration entry
+    text_sensor:
+      - platform: template
+        name: Uptime Human Readable
+        id: uptime_human
+        icon: mdi:clock-start
+    sensor:
+      - platform: uptime
+        name: Uptime Sensor
+        id: uptime
+        update_interval: 60s
+        on_raw_value:
+          then:
+            - text_sensor.template.publish:
+                id: uptime_human
+                state: !lambda |-
+                  int seconds = round(id(uptime).raw_state);
+                  int days = seconds / (24 * 3600);
+                  seconds = seconds % (24 * 3600);
+                  int hours = seconds / 3600;
+                  seconds = seconds % 3600;
+                  int minutes = seconds /  60;
+                  seconds = seconds % 60;
+                  return (
+                    (days ? String(days) + "d " : "") +
+                    (hours ? String(hours) + "h " : "") +
+                    (minutes ? String(minutes + "m " : "") +
+                    (String(seconds) + "s") 
+                  ).c_str();
+
 See Also
 --------