Adding support for blocks directory

[thagxt]

Adding support for Theme blocks

Warn Checklist

• This changes the interface and requires a Major/Minor version change.
• I have 🎩'd these changes by using the commands I changed by hand.
• I have added a dependency to the project.
• I have considered any potential impact on node-themekit

[thagxt]

I have signed the CLA!

[matt-thatworks]

Hello, when will you release a new version with blocks directory access?

[monting]

The project has been deprecated. But would be nice to release since it's just a folder.