fix(signature): add initial support for signatures

src/DCC.ts

@@ -75,6 +75,7 @@ export class DigitalCalibrationCertificateType extends DCCXMLElement {
   measurementResults: MeasurementResultListType;
   comment?: DCCXMLElement;
   document?: ByteDataType;
+  "ds:Signature"?: any;
 
   constructor(el: Partial<DigitalCalibrationCertificateType> = {}) {
     super(el);
@@ -82,6 +83,7 @@ export class DigitalCalibrationCertificateType extends DCCXMLElement {
     this.measurementResults = new MeasurementResultListType(el.measurementResults);
     if (el.comment) this.comment = new DCCXMLElement(el.comment);
     if (el.document) this.document = new ByteDataType(el.document);
+    if (el["ds:Signature"]) this["ds:Signature"] = el["ds:Signature"];
   }
 }