Add ctrlc crate documentation

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: brson

crates/rustmax/doc-src/crate-ctrlc.md

@@ -0,0 +1,41 @@
+Simple handling of Ctrl+C for CLI programs.
+
+- Crate [`::ctrlc`].
+- [docs.rs](https://docs.rs/ctrlc)
+- [crates.io](https://crates.io/crates/ctrlc)
+- [GitHub](https://github.com/Detegr/rust-ctrlc)
+
+---
+
+`ctrlc` provides a simple, cross-platform way to set a handler
+for the Ctrl+C signal (`SIGINT` on Unix, `CTRL_C_EVENT` on Windows).
+It spawns a dedicated signal-handling thread
+and invokes a user-provided closure when the signal is received.
+
+The typical pattern is to pair a handler with an [`AtomicBool`]
+that the main loop checks to know when to shut down gracefully.
+
+## Examples
+
+Graceful shutdown with an atomic flag:
+
+```rust,no_run
+use std::sync::Arc;
+use std::sync::atomic::{AtomicBool, Ordering};
+
+let running = Arc::new(AtomicBool::new(true));
+let r = running.clone();
+
+ctrlc::set_handler(move || {
+    r.store(false, Ordering::SeqCst);
+}).expect("Error setting Ctrl-C handler");
+
+while running.load(Ordering::SeqCst) {
+    // Do work...
+    break; // (break immediately for doctest)
+}
+
+println!("Shutting down.");
+```
+
+[`AtomicBool`]: std::sync::atomic::AtomicBool

crates/rustmax/src/lib.rs

@@ -354,9 +354,7 @@ pub mod comrak {
 
 #[cfg(feature = "ctrlc")]
 pub mod ctrlc {
-    //! Simple handling of CTRL-C for CLI programs.
-    //!
-    //! See crate [`::ctrlc`].
+    #![doc = include_str!("../doc-src/crate-ctrlc.md")]
 
     pub use ::ctrlc::*;
 }

src/linksubs.json5

@@ -104,6 +104,8 @@
     "api/crossbeam_utils/struct.Backoff.html",
     "crate::std::sync":
     "api/std/sync/index.html",
+    "std::sync::atomic::AtomicBool":
+    "api/std/sync/atomic/struct.AtomicBool.html",
     "crate::std::thread":
     "api/std/thread/index.html",
     "crate::std::sync::mpsc":