feat(maker-wix): Expose the property associateExtensions (#3674)

See here for documentation https://js.electronforge.io/classes/_electron_forge_maker_wix.InternalOptions.MSICreator.html#associateExtensions

Author: fras2560

packages/maker/wix/src/Config.ts

@@ -7,6 +7,10 @@ export interface MakerWixConfig {
    * your app by Squirrel.
    */
   appUserModelId?: string;
+  /**
+   * A comma separated string of extensions with each to be associated the app icon.
+   */
+  associateExtensions?: string;
   /**
    * The app's description
    */