Catch async exceptions

[kenodegard]

Previously we weren't actually catching the top-level async exceptions. We were doing this:

try {
    cli()
} catch (err) {
    if (err instanceof Error) setFailed(err)
    else throw err
}

But instead needed this:

cli().catch(err => {
    if (err instanceof Error) setFailed(err)
    else throw err
})

Nothing has functionally changed here we just catch the errors in a cleaner manner.