redoc-cli bundle downloaded spec filename and format

[natnan]

When one bundles specs into a static html, the download button downloads a "swagger.json". It would be neat to be able to:

• Change the filename
• And make it possible to download the file as yml. The source being yml doesn't help in this case.

Filename changing is possible by adding the following to the template:

    <script>
        document.addEventListener("DOMContentLoaded", (event) => {
            document.getElementsByClassName('sc-gipzik')[0].download = 'renamed_spec.json';
        });
    </script>

but not as pretty and future-proof as a parameter.