Add option to only run play or smoke tests

[josephnle]

What I did

• Adds an option --only-type <testType> that takes either play or smoke
• If the option is set, only Play or only Smoke tests will run.
• I couldn't figure out how to do this for stories json mode and as far as I know, I don't think this type of information is available in the stories.json?
• Happy to change the option name, wasn't sure what to call it 😅

How To Test

# Should only run play tests
yarn test-storybook --only-type play button
# Should only run smoke tests
yarn test-storybook --only-type smoke button

Closes #28