Error reporting

[9ary]

Currently, main returns a Result<(), Box<dyn Error>>, which means

• The exit code is always 0 or 1
• The error message is a debug print of the Error

Context is also not provided for errors. Use https://docs.rs/anyhow/latest/anyhow/.

Clap also calls exit(2) directly. try_parse should be used instead.

Using https://crates.io/crates/exitcode would be a good idea for informative exit codes.