Bump version to v0.28.0

In preparation for releasing `secp256k1-sys v0.9.0` and `secp256k1
v0.28.0` add changelog entries to both crates, bump the version of
`secp256k1` (`secp256k1-sys` was done already), and update the lock
files.

Author: tcharding

CHANGELOG.md

@@ -1,6 +1,10 @@
-# Unreleased
+# 0.28.0 - 2023-08-24
 
-* Bump MSRV to 1.48
+* Depend on recent release of `secp2561-sys`.
+* 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 +1,6 @@
-# Unreleased
+# 0.9.1
 
+* Update libsecp256k1 to v0.3.2 [#645](https://github.com/rust-bitcoin/rust-secp256k1/pull/645)
 * Bump MSRV to 1.48
 
 # 0.8.1 - 2023-03-16