Since #12241 we have notifications for this when the user navigates away from the viewer, but we do not yet warn when switching documents, which means that if you call e.g. `PDFViewerApplication.open` with a new document (or directly call `BaseViewer.setDocument` when using the viewer components standalone) there won't be any warning about losing form data. This should be addressed.
this.externalServices.reportTelemetry({
      type: "unsupportedFeature",
      featureId,
    });
    if (!this.triggerDelayedFallback) {
      this.triggerDelayedFallback = () => {
        this.fallback(featureId);
        this.triggerDelayedFallback = null;
      };
    }
  },
  fallback(featureId) {
    this.externalServices.reportTelemetry({
      type: "unsupportedFeature",
      featureId,
    });
    
    
    switch (featureId) {
      case UNSUPPORTED_FEATURES.errorFontLoadNative:
      case UNSUPPORTED_FEATURES.errorFontMissing:
        return;
    }
    
    
    if (this.fellback) {
      return;
    }