feat(#58): write to stdout if not tty

[AlejandroSuero]

When piping the command like freeze png.go | pbcopy it will write to the stdout.

Like @maaslalani said, when not tty it will write to stdout.

• feat(#58): add copy to clipboard flag --copy #97 (comment)

Demo

write-to-stdout-if-piped-demo.mp4

[AlejandroSuero]

In this demo I show how the current freeze png.go > out.txt won't write correctly to stdout when piped and how this PR's changes makes it possible to do it.

write-to-stdout-files-demo.mp4