Add a note on rustls in Cargo.toml

Specifically note that the dangerous_configuration feature is enabled
because we need it for quinn and the dummy TLS certificates.

Signed-off-by: Lee Smet <lee.smet@hotmail.com>

Cargo.toml

@@ -56,6 +56,8 @@ quinn = { version = "0.10.2", default-features = false, features = [
   "rustls",
   "tls-rustls",
 ] }
+# For now dangerous_configuration is needed to setup the certificate
+# verifier for the dummy quinn certificates.
 rustls = { version = "0.21.10", default-features = false, features = [
   "dangerous_configuration",
 ] }