Releases generated from markdown files

[JasonEtco]

Since releases aren't version controlled or PR-able (the content of the actual release), it'd be neat to have a .github/releases folder of markdown files. Maybe using front-matter, it could follow a scheme like this (taking options from octokit.repos.createRelease):

---
title: My dope release
tag: v1.0.0
---
This is the body of the release!

This could even pull in functionality similar to Release Drafter, and update the PR instead of the draft release.

Everything as code.