README,docs: point to Cargo.toml for features description

Author: wprzytula

README.md

@@ -64,6 +64,11 @@ The driver supports the following:
 
 For planned future improvements, see our [Milestones].
 
+### Feature flags
+The driver has several optional features that can be enabled or disabled in `Cargo.toml`.
+Refer to [scylla/Cargo.toml](https://docs.rs/crate/scylla/latest/source/Cargo.toml.orig)
+for the list of available features and their descriptions.
+
 ## Getting Help
 
 We invite you to discuss any issues and ask questions on the [ScyllaDB Forum] and the `#rust-driver` channel on [ScyllaDB Slack].

scylla/src/lib.rs

@@ -91,6 +91,11 @@
 //! # }
 //! ```
 //! See the [book](https://rust-driver.docs.scylladb.com/stable/statements/result.html) for more receiving methods.
+//!
+//! # Feature flags
+//! The driver has several optional features that can be enabled or disabled in `Cargo.toml`.
+//! Refer to [scylla/Cargo.toml](https://docs.rs/crate/scylla/latest/source/Cargo.toml.orig)
+//! for the list of available features and their descriptions.
 
 #![cfg_attr(docsrs, feature(doc_auto_cfg))]