Mention crypto features in README

Cargo.toml

@@ -25,13 +25,17 @@ rustls--aws_lc_rs = ["rustls/aws_lc_rs"] # default, but doesn't build everywhere
 rustls--ring = ["rustls/ring"] # more compatible, (e.g., easily builds on Windows)
 
 [dependencies]
-rustls = { version = "^0.23", default-features = false, features = ["std"] }
 rustls-webpki = "^0.102"
 
 [dependencies.log]
 version  = "^0.4"
 optional = true
 
+[dependencies.rustls]
+version          = "^0.23"
+default-features = false
+features         = ["std"]
+
 [dependencies.rustls-native-certs]
 version  = "^0.7"
 optional = true

README.md

@@ -9,6 +9,14 @@
 rustls-connector is a library aiming at simplifying using rustls as
 an alternative to openssl and native-tls
 
+## Warning about crypto backends
+
+A crypto implementation must be enabled in rustls using feature flags.
+We mimic what rustls does, providing one feature flag per implementation and enabling the same as rustls by default.
+Available options are:
+- `rustls--aws_lc_rs` (default)
+- `rustls--ring`
+
 ## Examples
 
 To connect to a remote server: