Added release notes for Djblets 1.0.2.

Review Request #9462 — Created Dec. 27, 2017 and submitted — Latest diff uploaded

Information

Djblets
release-1.0.x
dfbda7c...

Reviewers

This is a small bug fix and feature enhancement release focusing on
Django compatibility issues and better support for editing JSON content
in the database and more easily providing multi-DPI image srcsets.

Built the docs and looked through them. Checked for build and spelling
errors.