docs: Mention fastrand-contrib in documentation

Also, port some bits over from src/lib.rs to README.md

Signed-off-by: John Nunley <dev@notgull.net>

README.md

@@ -83,11 +83,16 @@ let rng = fastrand::Rng::new();
 let mut bytes: Vec<u8> = repeat_with(|| rng.u8(..)).take(10_000).collect();
 ```
 
+This crate aims to expose a core set of useful randomness primitives. For more niche algorithms, consider using the [`fastrand-contrib`] crate alongside this one.
+
 # Features
 
 - `std` (enabled by default): Enables the `std` library. This is required for the global
   generator and global entropy. Without this feature, [`Rng`] can only be instantiated using
-  the [`with_seed`](Rng::with_seed) method.
+  the [`with_seed`](https://docs.rs/fastrand/latest/fastrand/struct.Rng.html#method.with_seed) method.
+- `js`: Assumes that WebAssembly targets are being run in a JavaScript environment.
+
+[`fastrand-contrib`]: https://crates.io/crates/fastrand-contrib
 
 ## License
 

src/lib.rs

@@ -73,6 +73,9 @@
 //! let mut bytes: Vec<u8> = repeat_with(|| rng.u8(..)).take(10_000).collect();
 //! ```
 //!
+//! This crate aims to expose a core set of useful randomness primitives. For more niche algorithms,
+//! consider using the [`fastrand-contrib`] crate alongside this one.
+//!
 //! # Features
 //!
 //! - `std` (enabled by default): Enables the `std` library. This is required for the global
@@ -92,6 +95,7 @@
 //! entropy sources and seed the global RNG. If the `js` feature is not enabled, the global RNG will
 //! use a predefined seed.
 //!
+//! [`fastrand-contrib`]: https://crates.io/crates/fastrand-contrib
 //! [`getrandom`]: https://crates.io/crates/getrandom
 
 #![cfg_attr(not(feature = "std"), no_std)]