Add --write command to file

[EmmaRamirez]

Thank you so much for this tool -- I really appreciate that it has a simple to use CLI! However, one thing I noticed (and forgive me if it's somewhere in a documentation elsewhere, but I don't see README info for the CLI. If possible, I'd like to submit a PR to add a --write flag to the CLI so that users don't have use go into source code to see how to use it. Thanks!