Update readme link.

Author: EkardNT

README.md

@@ -27,7 +27,7 @@ Eventually you will be able to do so once support for running `parse` and `unwra
 
 | Feature name | Enabled by default? | Requires nightly? | Description |
 |---|---|---|---|
-| `tracked` | No | Yes | Use the unstable [proc_macro_tracked_env](https://github.com/rust-lang/rust/issues/74690) feature to inform the build system about the used environment variables. |
+| `tracked` | No | Yes | Use the unstable [proc_macro_tracked_env](https://github.com/rust-lang/rust/issues/99515) feature to inform the build system about the used environment variables. |
 
 ## Usage
 

const_env_tests/src/main.rs

@@ -1,3 +1,5 @@
+use std::sync::LazyLock;
+
 use const_env::{env_item, env_lit};
 
 const USIZE_ARRAY: [usize; 3] = env_lit!("INT_ARRAY", [1, 2, 3]);
@@ -68,6 +70,10 @@ static ORIGIN: Vec2<f64> = Vec2 { x: 0., y: 0. };
 
 static ORIGIN_LIT: Vec2<f32> = env_lit!("ORIGIN", Vec2 { x: 0., y: 0.});
 
+static FOO: LazyLock<u32> = LazyLock::new(|| {
+    option_env!("FOO").and_then(|foo| foo.parse().ok()).unwrap_or(0)
+});
+
 fn main() {
     assert_eq!([10, 11, 12], USIZE_ARRAY);
     assert_eq!(["bar"], STRING_ARRAY);