Add event category to robot as well (#125)

Author: alan412

src/toolbox/toolbox_robot.ts

@@ -1,5 +1,6 @@
  import * as common from './toolbox_common'
  import {category as hardwareCategory} from './hardware_category';
+ import {category as eventCategory} from './event_category';
 
  export function getToolboxJSON(
      shownPythonToolboxCategories: Set<string> | null) {
@@ -8,6 +9,7 @@
          kind: 'categoryToolbox',
          contents: [
             hardwareCategory,
+            eventCategory,
             { kind: 'sep' },
             ...common.getToolboxItems(shownPythonToolboxCategories)
          ]