feat: Create merge request with reviewers

- DMD-1263
- Mirrors reviewer assignment from PUT /merge-request/{id} to the create
  endpoint. createMergeRequest() and setReviewers() are wrapped in a
  transaction so invalid reviewers roll back the MR insert atomically.

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

Author: martinsifra

src/Keboola/StorageApi/Client.php

@@ -985,7 +985,8 @@ public function pullTableToBranch(string $tableId): string
      *     description?: ?string,
      *     externalId?: ?string,
      *     autoMergeStrategy?: ?string,
-     *     autoMergeAt?: ?string
+     *     autoMergeAt?: ?string,
+     *     reviewers?: list<int>
      * } $data
      * @return int - created MR id
      */