Exclude package-lock.json

[egmontkob]

https://pmarsceill.github.io/just-the-docs/package-lock.json

This file seems to contain technical info that are none of the business of the site's readers. What do you think of adding it by default to _config.yml's exclude section (perhaps as wildcard "package*.json")?

[pmarsceill]

Yeesh you're right. I didn't realize this was getting compiled. Thank you. I will add this to the next release.