zbus_macros-2.0.0-beta.2

New release to go with zbus 2.0.0-beta.2.

• dbus_proxy now generates async proxy code as well, that provides nearly identical API to existing sync proxy but async. An unfortunate side-affect of this change is that explicit lifetimes a now needed for Value. So this commit also addresses that in all examples/tests.
• Drop links to docs.rs from Cargo.toml file. The link for crates.io is automatically generated for us so specifying it manually could lead to link sending to latest stable release docs from an alpha or beta release page.
• Document zbus(header) attribute.
• Make API consistent wrt ObjectPath arguments. We've a specific type for object paths but for convenience we've been allowing string types to be passed as object paths that we internally convert to ObjectPath or OwnedObjectPath. However, we've been inconsistent on this practice and require ObjectPath to be passed by the user in some places. We now expect users to always pass something that can be converted into an ObjectPath, which includes both &str and String.
• Add span information to generated property getter. This results in more useful errror messages for things like https://gitlab.freedesktop.org/dbus/zbus/-/issues/135.
• Add Debug impl for Proxy types.
• Provide new_owned constructor for Proxy types.
• Change repo links to point to new cool location.