Header/Footer: Add graph (#12492)

source/lovelace/header-footer.markdown

@@ -76,3 +76,36 @@ entities:
       description: Override the entity image.
       type: string
 {% endconfiguration %}
+
+## Graph header & footer
+
+Widget to show an entity in the sensor domain as a graph in the header or footer.
+
+<p class='img'><img src='/images/lovelace/header-footer/graph.png' alt="Screenshot of an entities card with a graph footer.">
+Screenshot of an entities card with a graph footer.
+</p>
+
+```yaml
+footer:
+  type: graph
+  entity: sensor.outside_temperature
+  hours_to_show: 24
+  detail: 1
+```
+
+{% configuration header-footer %}
+entity:
+  required: true
+  description: Entity id of `sensor` domain
+  type: string
+detail:
+  required: false
+  description: Detail of the graph `1` or `2`, `1` equals one point/hour, `2` equals six points/hour
+  type: integer
+  default: 1
+hours_to_show:
+  required: false
+  description: Hours to show in graph
+  type: integer
+  default: 24
+{% endconfiguration %}