Variable: ForceResponsiveViewportFeature
• Const ForceResponsiveViewportFeature: FeatureClass<ForceResponsiveViewportOptions>
This feature inserts or, when present, replace a meta element looking like:
<meta name="viewport" content="width=device-width,initial-scale=1,minimum-scale=1,maximum-scale=1" />
This will guarantee that the layout viewport will match device-width (hence, “responsive”). Minimum scale is locked to 1, but you can customize maximum scale to allow pinch-zoom gestures (see ForceResponsiveViewportOptions). See also MDN—Using the viewport meta tag ...
example 
const Webshell = makeWebshell(
  WebView,
  new ForceResponsiveViewportFeature({
    maxScale: 3,
  })
);