Feat(cli): exit with non-zero code when there are diagnostics

[Boshen]

The current prototype always exit with 0 because I haven't implemented anything related to exit code.

In this good first issue, you will learn about the std::process::Termination trait and the std::process::ExitCode struct.

In oxc_cli, you may define a wrapper enum for all the possible exit states

#[derive(Debug)]
pub enum CliRunResult {
    None,
    PathNotFound {
        path: PathBuf,
    },
    LintResult {
        ... bunch of stats and stuff
    },
}

and nice messages inside the report method.

Finally inside main.rs, you can return the run result with std::process::Termination implemented on it.

fn main() -> CliRunResult {}

Have fun!

[thepassle]

this was implemented in #52 and #56