contracts: Release as v3.0.0 and add reserved field to ContractInfoOf (#8175)

* contracts: Update README

* contracts: Add CHANGELOG.md

* contracts: Bump version to v3.0.0 and allow publish

* Typos

Co-authored-by: Andrew Jones <ascjones@gmail.com>

* Improve wording in the changelog

* contracts: Add reserved field to ContractInfoOf for future proofing

* also bump frame-benchmarking

* update lockfile

Co-authored-by: Andrew Jones <ascjones@gmail.com>
Co-authored-by: Benjamin Kampmann <ben@parity.io>

substrate/frame/contracts/common/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "pallet-contracts-primitives"
-version = "2.0.1"
+version = "3.0.0"
 authors = ["Parity Technologies <admin@parity.io>"]
 edition = "2018"
 license = "Apache-2.0"
@@ -8,7 +8,6 @@ homepage = "https://substrate.dev"
 repository = "https://github.com/paritytech/substrate/"
 description = "A crate that hosts a common definitions that are relevant for the pallet-contracts."
 readme = "README.md"
-publish = false
 
 [package.metadata.docs.rs]
 targets = ["x86_64-unknown-linux-gnu"]