Expose version via `--version` flag

[timfallmk]

Just a minor request to expose the current running version via --version string. PR incoming.

[timfallmk]

It seems this is already handled, but only in cases where the binary is built via the official CI here (to get a valid version). It might make sense to set a reasonable default, but it seems like nitpick. I'll leave this open 24 hours for comment, and then close as "done".