build: add deploy workflow

[joyeecheung]

Tested on my fork: https://joyeecheung.github.io/package-examples/
Once merged, this will be published to https://nodejs.github.io/package-examples/

Refs: #17

[joyeecheung]

I think this should not land until we merge #16, otherwise the guide is not yet ready for publishing.

[joyeecheung]

I noticed that the title isn't configured correctly because .bookignore is ignoring, er, the configuration by mistake. Removed it from the ignore file.

[joyeecheung]

Landing it with the fix - I think that should be tiny enough without a re-review (before, the pages contains "HonKit" in the title because the configuration wasn't effective due to the ignore)

[joyeecheung]

This is now live: https://nodejs.github.io/package-examples/

Unpublishing my fork..