webpki-roots support

[QuietMisdreavus]

I'm looking to integrate hyper-proxy into egg-mode (see egg-mode-rs/egg-mode#101). However, i also recently had an issue reported where a user couldn't use the native certificate store as loaded by rustls-native-certs (see egg-mode-rs/egg-mode#92). I fixed this at the time by exposing a feature from hyper-rustls that made it use statically-linked certificates from the webpki-roots crate instead of rustls-native-certs. Would you be open to exposing a Cargo feature to switch between these certificate stores?

[tafia]

I'm definitely opened to it but I don't have much time to do it myself.

[QuietMisdreavus]

No worries! I'll try to work it in myself and post a PR.