Add state object detail to numeric state (#31809)

* Add state object detail to numeric state

The numeric state trigger populates an object called `state` but this was not in the documentation previously. This change makes it explicit and also provides a link to the relevant state object documentation.

* Update trigger.markdown

User more concise explanation of the state object in the numeric trigger, and added an example using `state.state`

* Update trigger.markdown

Added explanation to examples that use `state`

source/_docs/automation/trigger.markdown

@@ -257,7 +257,24 @@ automation:
 
 {% endraw %}
 
-More dynamic and complex calculations can be done with `value_template`.
+More dynamic and complex calculations can be done with `value_template`. The variable 'state' is the [state object](/docs/configuration/state_object) of the entity specified by `entity_id`.
+
+The state of the entity can be referenced like this:
+
+{% raw %}
+
+```yaml
+automation:
+  trigger:
+    - platform: numeric_state
+      entity_id: sensor.temperature
+      value_template: "{{ state.state | float * 9 / 5 + 32 }}"
+      above: 70
+```
+
+{% endraw %}
+
+Attributes of the entity can be referenced like this:
 
 {% raw %}