code: public function getSettingsHtml()
      {
          // Register our asset bundle
          Craft::$app->getView()->registerAssetBundle(WidthFieldtypeAsset::class);
  
          // Get our id and namespace
          $id = Craft::$app->getView()->formatInputId('width-fieldtype');
          $namespacedId = Craft::$app->getView()->namespaceInputId($id);
  
          Craft::$app->getView()->registerJs("new WidthSelectInput('{$namespacedId}');");
  
          // Render the settings template
          return Craft::$app->getView()->renderTemplate(
              'width-fieldtype/_components/fields/Width_settings',
              [
                  'field'        => $this,
                  'allOptions'   => array_keys(self::getOptions()),
                  'id'           => $id,
                  'namespacedId' => $namespacedId,
                  'settings'     => $this->settings,
              ]
          );
      }
docs: Returns the component’s settings HTML.
  
  @throws \Twig_Error_Loader
  @throws \yii\base\Exception
  
  @return string|null