Semver bump due to upstream oci-spec API change

Signed-off-by: David Steele <david.steele@alianza.com>

Author: dsteeley

Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "ocidir"
 description = "A Rust library for reading and writing OCI (opencontainers) layout directories"
-version = "0.5.0"
+version = "0.6.0"
 edition = "2024"
 license = "MIT OR Apache-2.0"
 repository = "https://github.com/containers/ocidir-rs"