docs(README.md): update backlog link to GitHub projects

The project backlog has been moved to GitHub projects as Waffle.io
is being shutdown.

The License badge has also been added to bring it inline with the
other repos.

Author: thestonefox

README.md

@@ -4,7 +4,7 @@
 > A collection of tools to simplify writing public API components for the Unity software.
 
 [![License][License-Badge]][License]
-[![Waffle][Waffle-Badge]][Waffle]
+[![Backlog][Backlog-Badge]][Backlog]
 
 ## Introduction
 
@@ -161,11 +161,11 @@ These materials are not sponsored by or affiliated with Unity Technologies or it
 
 [Malimbe-Image]: https://user-images.githubusercontent.com/1029673/48707109-4d876080-ebf6-11e8-9476-4f084246771d.png
 [License-Badge]: https://img.shields.io/github/license/ExtendRealityLtd/Malimbe.svg
-[Waffle-Badge]: https://badge.waffle.io/ExtendRealityLtd/Malimbe.svg?columns=Bug%20Backlog,Feature%20Backlog,In%20Progress,In%20Review
+[Backlog-Badge]: https://img.shields.io/badge/project-backlog-78bdf2.svg
 [Version-Release]: https://img.shields.io/github/release/ExtendRealityLtd/Malimbe.svg
 [Version-Prerelease]: https://img.shields.io/github/release-pre/ExtendRealityLtd/Malimbe.svg?label=pre-release&colorB=orange
 
-[Waffle]: https://waffle.io/ExtendRealityLtd/Malimbe
+[Backlog]: http://tracker.vrtk.io
 [Releases]: ../../releases
 [SemVer]: https://semver.org/
 [VCS]: https://en.wikipedia.org/wiki/Version_control