Snowflake needs outbound proxy support

For continued iOS support, we will need to run Snowflake behind a proxy, since with its Go runtime it's way to big to run in a Network Extension, which has a hard 15 MByte RAM usage limit.

Currently, Snowflake doesn't seem to support that scenario.

Please point me to the code, if it actually has, so I can understand how to leverage it.

If not, I suggest having a look at Obfs4proxy for reference on how this could be implemented:

https://gitlab.com/yawning/obfs4/-/blob/master/obfs4proxy/obfs4proxy.go#L67-158

Thank you!