Refine schema for forbid-dom-props options

Author: davazp

lib/rules/forbid-dom-props.js

@@ -28,11 +28,13 @@ module.exports = {
         forbid: {
           type: 'array',
           items: {
-            type: 'string'
-          }
+            type: 'string',
+            minLength: 1
+          },
+          uniqueItems: true
         }
       },
-      additionalProperties: true
+      additionalProperties: false
     }]
   },