Update the documentation for connect() method to include the actual information of the TLS features

[alpha-tango-kilo]

Hi there!

I've just started using Tungstenite and ran into an issue trying to support secure sockets.

The documentation says that to support WSS, you need to use native-tls or rustls-tls feature flags. I wanted to use the latter, but I noticed that the feature flag rustls-tlsdoesn't exist anymore. This led me to guess correcting it to rustls, which works because Cargo makes optional dependencies available as features implicitly (not something I'm a fan of, but here we are). However, this then meant that while everything compiled and ran, I would always have my connection refused with 400: bad request. Everything worked once I changed my feature selection to rustls-tls-webpki-roots, but it took a lot of head-scratching to work out that was the solution, as I hadn't used websockets before and didn't know what was going wrong (was it me, the API, or the library?).

A couple suggestions off the back of my experience, if I may:

• Update the connect documentation to include the up-to-date rustls-related feature flags
• Consider maybe triggering a compile error if compiling with not all the dependencies of a valid feature selection e.g. compiling with rustls but not webpki

I could look to write the PR if you'd like, just wanted to know your thoughts first :)

[daniel-abramov]

We've documented the usage of features in the README 🙂 Unfortunately we've forgotten to update the documentation on connect(). E.g. we need to update it, thanks for noticing it.