fix(dcc): add missing attributes

src/DCCDocument.ts

 import { Element, js2xml, xml2js } from "xml-js";
 
 import { DigitalCalibrationCertificateType, DCC } from "./DCC";
+import { DSI } from "./DSI";
 
 export class DCCDocument {
   _declaration: unknown;
@@ -15,6 +16,10 @@ export class DCCDocument {
     return new DCCDocument({
       digitalCalibrationCertificate: new DigitalCalibrationCertificateType({
         _attr: {
+          "xmlns:xsi": "http://www.w3.org/2001/XMLSchema-instance",
+          "xsi:schemaLocation": `${DCC.namespaceUrl} ${DCC.schemaLocation}`,
+          "xmlns:dcc": DCC.namespaceUrl,
+          "xmlns:si": DSI.namespaceUrl,
           schemaVersion: DCC.schemaVersion,
         },
       }),