Add "application/zip" to "allowed-mime-types" in dbp-file-source

Local test is ok, not sure if this mime type is sufficient (application/octet-stream ?)

src/dbp-official-signature-pdf-upload.js

@@ -775,7 +775,7 @@ class OfficialSignaturePdfUpload extends ScopedElementsMixin(DBPSignatureLitElem
                         <dbp-file-source
                             id="file-source"
                             context="${i18n.t('qualified-pdf-upload.upload-field-label')}"
-                            allowed-mime-types="application/pdf"
+                            allowed-mime-types="application/pdf,application/zip"
                             enabled-sources="local${this.showTestNextcloudFilePicker ? ",nextcloud" : ""}"
                             nextcloud-auth-url="${this.nextcloudWebAppPasswordURL}"
                             nextcloud-web-dav-url="${this.nextcloudWebDavURL}"