some links added

src/lib.rs

@@ -25,7 +25,7 @@
 //!
 //! Default features:
 //!
-//!  - `std`: Enables functionality relying on the standard library.
+//!  - [`std`](https://doc.rust-lang.org/std/): Enables functionality relying on the standard library.
 //!  - [`alloc`](https://doc.rust-lang.org/alloc/): Enables features which operate on containers
 //!     like [`alloc::vec::Vec`](https://doc.rust-lang.org/beta/alloc/vec/struct.Vec.html).
 //!     Enabled by the `std` features.