add example + integration tests for UA emulation

[GlenDC]

could just integrate it into the mitm proxy example aleady
but also add an example just for a client hardcoded with a specific profile that we could test the hash for (e.g. macos firefox

The integration tests test some more profiles and also check for the hash to see if get the right tls + http fingerprint. Doesn't tell the whole story but it's a beginning of some guarantees at least.