Make bash-tool work in the browser

What's the hold up? Anything I can do to help?

@tamlyn Why would you want this?

For political reasons, we don't have any suitable server side infrastructure on which to deploy long running agents, so I've built an agent harness that runs in the browser with a virtualized file system and just-bash. For the time being I've created my own agent tools, but I'd rather just use the full bash-tool package.

Would you be able to test this PR? My issue is that I have no way of testing whether it works