use pflag to keep argument style unified with tsc

[trim21]

in tsc we have flags with double dash like --noEmit. but in tsgo it's single dash -noEmit now.

maybe use https://pkg.go.dev/github.com/spf13/pflag to preserve the old arguments style?

[jakebailey]

This is a temporary CLI: #492

We have our own CLI parser that matches tsc that will be used long-term.