Add release notes template.

.github/release_template.md

@@ -0,0 +1,25 @@
+# What Changed In This Release
+
+[High-level, colloquial summary of changes—mandatory]
+
+## New Features
+
+-
+
+## Enhancements
+
+-
+
+## Bug Fixes
+
+-
+
+## Other Changes
+
+-
+
+## Notes & Caveats
+
+-
+
+## Acknowledgments