cli: Add --version (#129)

Since it's useful.

Signed-off-by: Colin Walters <walters@verbum.org>

Author: cgwalters

crates/kit/src/main.rs

@@ -42,6 +42,7 @@ pub const CONTAINER_STATEDIR: &str = "/var/lib/bcvk";
 /// install them to disk, or manage existing installations - all without
 /// requiring root privileges.
 #[derive(Parser)]
+#[command(version)]
 struct Cli {
     #[command(subcommand)]
     command: Commands,