Add instructions to set up a snowflake standalone proxy to community pages

We discussed improving the instructions for setting up and running a Go standalone proxy for Snowflake in tpo/anti-censorship/pluggable-transports/snowflake#40031

We'd like to run a campaign to get more standalone snowflakes in the hopes of getting a higher ratio of unrestricted NATs at some point and this is a prerequisite for that.

Is it possible to create a page linked from https://community.torproject.org/relay/setup/ with detailed instructions (not sure if that's the best place since they aren't relays exactly).