Bump version to v0.23.1

We just applied a hot fix to the 0.23.0 released code to fix the
features enabled in `rand` when our "rand-std" feature is enabled. This
requires a bump of the patch version for release.

Bump the version and add a changelog entry.

Author: tcharding

CHANGELOG.md

@@ -1,3 +1,7 @@
+# 0.23.1 - 2022-06-24
+
+[Enable "rand/std_rng" feature](https://github.com/rust-bitcoin/rust-secp256k1/pull/460) when the crate's "rnd-std" feature is enabled.
+
 # 0.23.0 - 2022-06-21
 
 The major change in this version is the increase of the Minimum Supported Rust Version (MSRV) from 1.29 to 1.41.1, this is a big change because it introduces Rust Edition 2018 to the codebase along with all the benefits that brings.

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "secp256k1"
-version = "0.23.0"
+version = "0.23.1"
 authors = [ "Dawid Ciężarkiewicz <[email protected]>",
             "Andrew Poelstra <[email protected]>" ]
 license = "CC0-1.0"