Add example code to use Snowflake based bridges in arti-client
Problem to solve
Currently, bridge docs are limited to one example using obfs4, whereas there are also Snowflake-based bridges which could be used by a prospective developer in their program.
Not having a Snowflake example just adds more friction for their use, especially in a brand-new API which doesn't have much outside documentation or usage.
Having a basic config written in the example code given for
BridgesConfig using the default torproject.org broker for Snowflake proxies would go a long way towards boosting adoption of Snowflake.
Add one more bridge in the example code which instead makes the connection via Snowflake. The rest of the code would be mostly unchanged.