io: Make error module public and re-export errors no-inline

diff --git a/io/src/error.rs b/io/src/error.rs
index 4cfdd289..aac4012e 100644
--- a/io/src/error.rs
+++ b/io/src/error.rs
@@ -1,5 +1,7 @@
 // SPDX-License-Identifier: CC0-1.0
 
+//! Error types for the `io` crate.
+
 #[cfg(feature = "alloc")]
 #[cfg(not(feature = "std"))]
 use alloc::boxed::Box;
@@ -201,6 +203,42 @@ define_errorkind!(
     Other
 );
 
+/// An error that can occur when reading and decoding from a buffered reader.
+#[derive(Debug)]
+pub enum ReadError<D> {
+    /// An I/O error occurred while reading from the reader.
+    Io(Error),
+    /// The decoder encountered an error while parsing the data.
+    Decode(D),
+}
+
+impl<D: fmt::Display> fmt::Display for ReadError<D> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::Io(e) => write!(f, "I/O error: {}", e),
+            Self::Decode(e) => write!(f, "decode error: {}", e),
+        }
+    }
+}
+
+#[cfg(feature = "std")]
+impl<D> std::error::Error for ReadError<D>
+where
+    D: fmt::Debug + fmt::Display + std::error::Error + 'static,
+{
+    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
+        match self {
+            Self::Io(e) => Some(e),
+            Self::Decode(e) => Some(e),
+        }
+    }
+}
+
+#[cfg(feature = "std")]
+impl<D> From<Error> for ReadError<D> {
+    fn from(e: Error) -> Self { Self::Io(e) }
+}
+
 #[cfg(feature = "alloc")]
 #[cfg(not(feature = "std"))]
 mod sealed {
diff --git a/io/src/lib.rs b/io/src/lib.rs
index 8212135e..ee45dc83 100644
--- a/io/src/lib.rs
+++ b/io/src/lib.rs
@@ -33,7 +33,7 @@ pub extern crate hashes;
 
 #[cfg(feature = "std")]
 mod bridge;
-mod error;
+pub mod error;
 
 #[cfg(feature = "hashes")]
 mod hash;
@@ -48,7 +48,8 @@ use std::vec::Vec;
 use encoding::{Decodable, Decoder, Encoder};
 
 #[rustfmt::skip]                // Keep public re-exports separate.
-pub use self::error::{Error, ErrorKind};
+#[doc(no_inline)]
+pub use self::error::{Error, ErrorKind, ReadError};
 #[cfg(feature = "std")]
 pub use self::bridge::{FromStd, ToStd};
 #[cfg(feature = "hashes")]
@@ -613,42 +614,6 @@ where
     decoder.end().map_err(ReadError::Decode)
 }
 
-/// An error that can occur when reading and decoding from a buffered reader.
-#[derive(Debug)]
-pub enum ReadError<D> {
-    /// An I/O error occurred while reading from the reader.
-    Io(Error),
-    /// The decoder encountered an error while parsing the data.
-    Decode(D),
-}
-
-impl<D: core::fmt::Display> core::fmt::Display for ReadError<D> {
-    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
-        match self {
-            Self::Io(e) => write!(f, "I/O error: {}", e),
-            Self::Decode(e) => write!(f, "decode error: {}", e),
-        }
-    }
-}
-
-#[cfg(feature = "std")]
-impl<D> std::error::Error for ReadError<D>
-where
-    D: core::fmt::Debug + core::fmt::Display + std::error::Error + 'static,
-{
-    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
-        match self {
-            Self::Io(e) => Some(e),
-            Self::Decode(e) => Some(e),
-        }
-    }
-}
-
-#[cfg(feature = "std")]
-impl<D> From<Error> for ReadError<D> {
-    fn from(e: Error) -> Self { Self::Io(e) }
-}
-
 #[cfg(feature = "std")]
 include!("../../include/newtype.rs"); // Explained in `REPO_DIR/docs/README.md`.