Added new featured blog post section to home page

Created by: ryan-blunden

We urgently need a mechanism to promote the most important blog posts to home page visitors so I created a new "featured blog posts" section on the home page.

It's a bit of a blunt tool and the list is totally manual to update, but this is a good thing for now, as it's easy to update, easy to sculpt the title and description for best visual display, and doesn't require changing anything for the blog posts themselves.

Preview at https://deploy-preview-657--sourcegraph.netlify.com/