Bump version to 0.12.0

Author: cberner

Cargo.toml

@@ -5,7 +5,7 @@ homepage = "https://www.redb.org"
 repository = "https://github.com/cberner/redb"
 readme = "README.md"
 license = "MIT OR Apache-2.0"
-version = "0.11.0"
+version = "0.12.0"
 edition = "2021"
 rust-version = "1.65"
 authors = ["Christopher Berner <christopherberner@gmail.com>"]