Support command-line flags

[nabadger]

Should we look at using something like https://github.com/spf13/viper

One of the issues I keep having is trying to remember the environment vars that klar supports ;)

Something like viper would support command line flags, environment vars, config files, and would also be self-documenting (via --help).

Good idea?

[hashmap]

Totally! We had like 2 env vars in the beginning.

[nabadger]

Cool, I'll work on a PR soon 👍