Migrate the embedded snowflake client to another URL

After deploying the new version of snowflake.torproject.org I realized that previously, this URL was also hosting an actual snowflake client, at snowflake.torproject.org/embed.html, in addition to the website. So, with the new website now deployed in place of the old one, the snowflake client is gone.

I think we should consider hosting this client on another URL, eg. client.snowflake.torproject.org or something like that, so that the actual snowflake bits are fully decoupled from the website.

This would also open up the possibility of setting up the https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake-webext project with a CI/CD pipeline.

For the time being, I've manually copied the snowflake client build from the old website to the new one and disabled deploying the website to production so that we avoid removing these files by accident as we figure out the next steps.