Add release notes for version 1.3.1

Added release notes for version 1.3.1, including changes to KubeJS, buildscript, and Milestones.

Author: ThePansmith

CHANGELOG.md

@@ -4,6 +4,12 @@
 ### Changes
 - Sample Text
 
+## [1.3.1]
+### Changes
+- Cleaned out KubeJS and config folders for easier importing
+- Fixed buildscript not working with projects that have a space in their name
+- Made Milestones opt in
+
 ## [1.3.0]
 ### Changes
 - Overhauled the repository, now using pakku as a basis along some various other helpful scripts