Missing instructions for adding a post

[beechnut]

There's no "Contributing" section in this README, which is the first place people look for guidance on contributing. There's a CONTRIBUTING.md file, but there's enough files in the project root that it's easy to overlook.

Definition of done

• a "Contributing" section in the README that references any other instructions

[juliaklindpaintner]

Noting that we will likely revise this ticket. We acknowledge that the instructions for adding a blog post should be documented, but don't necessarily think it should be added to a Contributing section in the README since we're not asking the general public viewing the repo to contribute to the blog.

[edwintorres]

Can we clarify the ask here a little bit more? @beechnut is about blog posts or contributing to the 18F site.

[beechnut]

I'd say the user story is something like: As a new member of 18F who wants to contribute a blog post or an update to the site, I want to figure out relatively quickly how to start contributing.

The current language in the README is a lot of context, but nothing that points the person: here's where to go to start a blog posts, here's where to go to update the site.