message: fix(omemo): bundle structure
  fix nextcloud/jsxc.nextcloud#146
diff: @@ -54,6 +54,9 @@ export default class Bundle {
  .t(ArrayBufferUtils.toBase64(this.bundle.identityKey.getPublic()))
  .up();
  + xmlBundle
  + .c('prekeys');
  +
  for (let preKey of this.bundle.preKeys) {
  xmlBundle
  .c('preKeyPublic', {
  @@ -63,6 +66,8 @@ export default class Bundle {
  .up();
  }
  + xmlBundle.up();
  +
  return xmlBundle;
  }
  