zvariant-2.3.0

• Fix Dictionary serialization for GVariant format.
• Derive Eq, Hash, on OwnedObjectPath to allow use as a HashMap key.
• Add API for efficient slicing of signature strings.
• Add API for efficient building of Structure instances.
• Deprecate existing Structure creation API.
• Drop a bunch of allocations from deserialization code.
• Add GVariant to crate description.
• Minor improvements to docs.

All contributors:

• @TimSmall
• @zeenix