Bump version to v0.28.0

Prepare for release by doing:

- Add changelog entry to `secp256k1-sys` for the recent version bump ready
  for release.
- Bump the version of secp256k1 to 0.28.0
- Add changelog entry to `secp256k1` for the imminent release.

Author: tcharding

CHANGELOG.md

@@ -1,6 +1,9 @@
-# Unreleased
+# 0.28.0 - 2023-10-02
 
-* Bump MSRV to 1.48
+* Depend on recent release of `bitcoin_hashes` v0.13.0 [#621](https://github.com/rust-bitcoin/rust-secp256k1/pull/621)
+* Add a verify function to `PublicKey` [#618](https://github.com/rust-bitcoin/rust-secp256k1/pull/618)
+* Add serialize function for schnorr::Signature [#607](https://github.com/rust-bitcoin/rust-secp256k1/pull/607)
+* Bump MSRV to 1.48 [#595](https://github.com/rust-bitcoin/rust-secp256k1/pull/595)
 * Remove implementations of `PartialEq`, `Eq`, `PartialOrd`, `Ord`, and `Hash` from the
   `impl_array_newtype` macro. Users will now need to derive these traits if they are wanted.
 

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "secp256k1"
-version = "0.27.0"
+version = "0.28.0"
 authors = [ "Dawid Ciężarkiewicz <[email protected]>",
             "Andrew Poelstra <[email protected]>" ]
 license = "CC0-1.0"

secp256k1-sys/CHANGELOG.md

@@ -1,5 +1,7 @@
-# Unreleased
+# 0.9.0 - 2023-10-02
 
+* Add bindings to the ElligatorSwift implementation [#627](https://github.com/rust-bitcoin/rust-secp256k1/pull/627)
+* Update vendored lib secp256k1 to v0.4.0 [#653](https://github.com/rust-bitcoin/rust-secp256k1/pull/653)
 * Bump MSRV to 1.48
 
 # 0.8.1 - 2023-03-16