fix: To unstable feature

Author: k-nasa

src/io/stderr.rs

@@ -119,6 +119,8 @@ impl Stderr {
     /// #
     /// # Ok(()) }) }
     /// ```
+    #[cfg_attr(feature = "docs", doc(cfg(unstable)))]
+    #[cfg(any(feature = "unstable", feature = "docs"))]
     pub async fn lock(&self) -> StderrLock<'static> {
         static STDERR: Lazy<std::io::Stderr> = Lazy::new(std::io::stderr);
 

src/io/stdin.rs

@@ -175,6 +175,8 @@ impl Stdin {
     /// #
     /// # Ok(()) }) }
     /// ```
+    #[cfg_attr(feature = "docs", doc(cfg(unstable)))]
+    #[cfg(any(feature = "unstable", feature = "docs"))]
     pub async fn lock(&self) -> StdinLock<'static> {
         static STDIN: Lazy<std::io::Stdin> = Lazy::new(std::io::stdin);
 

src/io/stdout.rs

@@ -119,6 +119,8 @@ impl Stdout {
     /// #
     /// # Ok(()) }) }
     /// ```
+    #[cfg_attr(feature = "docs", doc(cfg(unstable)))]
+    #[cfg(any(feature = "unstable", feature = "docs"))]
     pub async fn lock(&self) -> StdoutLock<'static> {
         static STDOUT: Lazy<std::io::Stdout> = Lazy::new(std::io::stdout);