Add deprecation note to README

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "cstr"
-version = "0.2.11"
+version = "0.2.12"
 authors = ["Xidorn Quan <me@upsuper.org>"]
 description = "Macro for building static CStr reference"
 repository = "https://github.com/upsuper/cstr"

README.md

@@ -6,12 +6,20 @@
 
 <!-- cargo-sync-readme start -->
 
+**This crate has been deprecated.
+Rust 1.77.0 stabilized [C-string literals][c-string-literal].
+From that version, `c"abc"` can be used in place of `cstr!("abc")` provided by this crate.
+This new feature gives more concise code and faster compilation.
+Hence, this crate will no longer be maintained.**
+
+[c-string-literal]: https://blog.rust-lang.org/2024/03/21/Rust-1.77.0.html#c-string-literals
+
 A macro for getting `&'static CStr` from literal or identifier.
 
 This macro checks whether the given literal is valid for `CStr`
 at compile time, and returns a static reference of `CStr`.
 
-This macro can be used to to initialize constants.
+This macro can be used to initialize constants.
 
 ## Example
 

src/lib.rs

@@ -1,9 +1,17 @@
+//! **This crate has been deprecated.
+//! Rust 1.77.0 stabilized [C-string literals][c-string-literal].
+//! From that version, `c"abc"` can be used in place of `cstr!("abc")` provided by this crate.
+//! This new feature gives more concise code and faster compilation.
+//! Hence, this crate will no longer be maintained.**
+//!
+//! [c-string-literal]: https://blog.rust-lang.org/2024/03/21/Rust-1.77.0.html#c-string-literals
+//!
 //! A macro for getting `&'static CStr` from literal or identifier.
 //!
 //! This macro checks whether the given literal is valid for `CStr`
 //! at compile time, and returns a static reference of `CStr`.
 //!
-//! This macro can be used to to initialize constants.
+//! This macro can be used to initialize constants.
 //!
 //! ## Example
 //!