renamed games folder to entries folder (also contained frameworks, libraries, ...) and added to the backlog

entries/doomsday_engine.md

@@ -0,0 +1,18 @@
+# Doomsday Engine
+
+_Remake of Doom, Doom II, Heretic, Hexen._
+
+- Home: http://dengine.net/, https://sourceforge.net/projects/deng/
+- State: mature
+- Download: https://sourceforge.net/projects/deng/files/
+- Platform: Windows, Linux, macOS
+- Keywords: action, commercial content, inspired by Doom + Doom II + Heretic + Hexen, remake, requires original content
+- Code repository: https://github.com/skyjake/Doomsday-Engine.git, https://git.code.sf.net/p/deng/code (+), http://hg.code.sf.net/p/deng/code-0 (hg)
+- Code language: C, C++
+- Code license: GPL-2.0 (see source files), GPL-3.0, LGPL-3.0 (core)
+
+Mixed license usage.
+
+## Building
+
+- Build system: CMake