[CLI] Prompt to add the release tag

[jhnstn]

This adds a prompt before creating the release tag on Gutenberg.

The --no-tag flag still works as before but now without that flag the script will prompt to tag Gutenberg after it pushes up the release branch

Testing

Follow the Testing guide to set up the tool to use forked repos.

• Run go run main.go release prepare gb {version} --no-tag and confirm that the rnmobile/{version} tag is not created on the forked repo
• Run go run main.go release prepare gb {version} and cancel the prompt to tag the release. Confirm that the tag is not created on the forked repo
• Run go run main.go release prepare gb {version} and confirm creating the release tag. Confirm that the tag is created on the forked repo

[derekblank]

I was able to follow the testing instructions on my forked repos. LGTM. 🚀