Add addon API test

types/dwt/dwt-tests.ts

@@ -99,3 +99,13 @@ function downloadImage() {
     DWObject.HTTPDownload("www.dynamsoft.com", "img.png", () => {}, (errorCode: number, errorString: string) => {});
   }
 }
+
+function loadPDF() {
+    const DWObject = Dynamsoft.WebTwainEnv.GetWebTwain('dwtcontrolContainer');
+    if (DWObject) {
+        DWObject.Addon.PDF.SetResolution(200);
+        DWObject.Addon.PDF.SetConvertMode(1);
+        DWObject.IfShowFileDialog = true;
+        DWObject.LoadImageEx(" ", 5);
+    }
+}