cleanup of keywords, a few new additions from the backlog

entries/duality.md

@@ -0,0 +1,10 @@
+# Duality
+
+- Home: https://www.duality2d.net/
+- State: mature
+- Keyword: game engine, 2D
+- Code repository: https://github.com/AdamsLair/duality.git
+- Code language: C#
+- Code license: MIT
+
+## Building