Refactoring: add more types to special visualisations arguments

src/UI/Popup/HistogramViz.ts

@@ -14,6 +14,7 @@ export class HistogramViz extends SpecialVisualization {
     args = [
         {
             name: "key",
+            type:"key",
             doc: "The key to be read and to generate a histogram from",
             required: true,
         },