Use non-Markdown license file (LICENSE.txt) for Bazel toolchains

Starting with `aspect_rule_js` 3.0.0, Markdown files are stripped by default in the Bazel toolchain. Gerrit Code Review relies on this toolchain for collecting [license](https://review.opendev.org/Documentation/js_licenses.html) files. As a result, packages that only ship a `LICENSE.md` file are missing from the aggregated license output. In Gerrit’s dependency tree, this currently affects only this package. All other dependencies already provide license files in non-Markdown formats (e.g. `LICENSE`, `LICENSE.txt`), which are correctly picked up. Would it be possible to also ship the license as `LICENSE.txt` (or a non-Markdown equivalent), so it is included in Bazel-based license collection? For context: - Bazel toolchain: aspect_rule_js 3.0.0 (Markdown stripping behavior) - Related [change](https://github.com/aspect-build/rules_js/commit/f62a25e061684bbdeb99302ebea32c0a05064ad1) - Related [issue](https://github.com/aspect-build/rules_js/issues/2806)