Add expand_legend option to graph cards

source/_dashboards/history-graph.markdown

@@ -71,6 +71,11 @@ fit_y_data:
   description: If true, configured Y-axis bounds would automatically extend (but not shrink) to fit the data.
   type: boolean
   default: false
+expand_legend:
+  required: false
+  description: If true, the legend will show all items initially
+  type: boolean
+  default: false
 {% endconfiguration %}
 
 ### Options for entities

source/_dashboards/statistics-graph.markdown

@@ -87,6 +87,11 @@ fit_y_data:
   description: If true, configured Y-axis bounds would automatically extend (but not shrink) to fit the data.
   type: boolean
   default: false
+expand_legend:
+  required: false
+  description: If true, the legend will show all items initially
+  type: boolean
+  default: false
 energy_date_selection:
   required: false
   description: If true, chart date range will follow the date selected on an `energy-date-selection` card on the same view, similar to energy cards.