Add Chef

[waldyrious]

Open core product: https://github.com/chef/chef, https://docs.chef.io/chef_license.html.

Open development process: and https://docs.chef.io/community_contributions.html.

No explicit openness pledge though. The about page is titled "Our Mission and Values", but makes no mention of, for instance, their open source products.

[waldyrious]

Since there isn't an unambiguous match to the current criteria (particularly no explicit openness pledge), let's put this on hold until a decision is reached in #44.

[wavyago]

Letsgo