This updates to a yet-to-be-released version of `gix` to be able to
leverage full local-time support thanks to the usage of `jiff`.
This means we can now rely on the local `now()` that `gix` signatures
come with, which naturally respect environment variables that help
to make commits statically known.
For the running Tauri application this won't have an effect as it won't
inherit environment variables, but the CLI will be different in that regard.
This also needs the ability to create commits.
Also experiment with `async` tauri commands, but without actually making
them `async` - nothing actually is so why pretend?
Further, assure we get the correct author and committer which helps it
pick up the overridden author information when creating a commit.