Set html_root_url to docs.rs

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "itoa"
-version = "0.3.1"
+version = "0.3.1" # remember to update html_root_url
 authors = ["David Tolnay <dtolnay@gmail.com>"]
 license = "MIT/Apache-2.0"
 description = "Fast functions for printing integer primitives to an io::Write"

src/lib.rs

@@ -6,6 +6,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+#![doc(html_root_url = "https://docs.rs/itoa/0.3.1")]
+
 use std::{io, mem, ptr, slice};
 
 #[inline]