Mounting "tar indexed" file images from JS

[gergness]

From R, it's possible to mount the ".tar.gz" files with the metadata added via rwasm::add_tar_index(), but I haven't been able to from javascript's webR.FS.mount. Looking closer at the documentation, I only see an example with the separate metadata, am I missing something, or any way to access the webr package's extraction tools from JS?

I'm new enough at JS that I don't know a way to give a self contained example, but I'm essentially trying this:

                const response = await fetch("/file.tar.gz);

                const options = {
                  packages: [{
                    blob: await response.blob(),
                    //metadata: await metadata.json(),
                  }],
                }
                await webR.FS.mount("WORKERFS", options, '/path');

(My ultimate goal is to parallelize the HTTP requests to see if it will be faster, so I want to use JS fetch instead of webr::mount() which does sequential HTTP requests)