Dynamically loading resources in loadPropertyPaneResources

loadPropertyPaneResources.ts

/**
 * Load property pane resources
 */
protected async loadPropertyPaneResources(): Promise<void> {
  PropertyPaneHelpers.setSpinner({
    bgColor: "white",
    spinnerProps: {
      getStyles: () => {
        return {
          circle: {
            height: 80,
            width: 80
          }
        };
      }
    }
  });

  // Write here the code you want to add to load your resources

  PropertyPaneHelpers.clearSpinner(200);
}