Update hacs.json for attribute improvements

For consistency with Localvolts naming of the field, "last_interval" attribute is now named "intervalEnd"
A new attribute "lastUpdate" has been added which indicates what time the most recent data was successfully retrieved.  
This is useful in determining how far into the interval the new price data has been retrieved.

hacs.json

@@ -1,7 +1,7 @@
 {
   "name": "Localvolts Integration",
   "documentation": "https://github.com/gurrier/localvolts",
-  "version": "0.2.2",
+  "version": "0.2.3",
   "render_readme": true,
   "content_in_root": false,
   "category": "integration"