Some initial work to get this moving to JavaScript. I haven't had time to test this out.

This fixes #21 I also see it as a good opportunity to update the documentation for to fix #22

Remaining work:

• Testing
• If you are running this action inside an organization or user repository (named username/username.github.io) it will deploy to the master branch instead.
• Documentation updates
• New screenshots

Thoughts

• This is a breaking change, suggested v1.0.0
• I have tried to keep the code as close to the original shell script in entrypoint.sh
• I tweaked some of the language in the README.md to remove bias.

Any feedback is welcome, thanks!