Improvements to docs.chef.io - content snapshots

Ohai Chefs!

As part of our work to make Chef documentation easier to use and contribute to, we have recently made additional changes that involve our scoped doc sets (e.g. https://docs.chef.io/release/12-10).

We created a new site, https://docs-archive.chef.io, that contains snapshots of the release content and then we removed those doc sets from the main doc site and the chef-web-docs repo. This allows us to clean up the user experience and flow on the main doc site (as part of our version-aware content strategy). A link to the archive site has been placed at the bottom of the left nav and links back to the main doc site are also on the archive site.

We hope you like the clean up and the changes!