add duke-nukem related topics

topics/build-engine/index.md

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+---
+display_name: Build Engine
+short_description: The Build Engine is game engine created by Ken Silverman, best known for powering Duke Nukem 3D.
+aliases: build1,build2,duke-nukem-3d-engine,con-script,con-files
+wikipedia_url: https://en.wikipedia.org/wiki/Build_(game_engine)
+related: duke-nukem,blood,shadow-warrior
+topic: build-engine
+---

topics/serious-engine/index.md

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+---
+display_name: Serious Engine
+aliases: croteam-engine,serious-editor,serious-sam-engine
+short_description: Serious Engine is a game engine created by croteam for serious sam games.
+related: serious-sam,the-talos-principle
+topic: serious-engine
+---
+Serious Engine is a 2001 game engine created by croteam and published by devolver digital used for serious sam games.

topics/southpaw-engine/index.md

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+---
+display_name: Southpaw Engine
+short_description: The southpaw is a game engine created by torus games.
+aliases: doom-advance,duke-nukem-advance
+related: doom-gba, dukenukem-gba
+topic: southpaw-engine
+---
+The southpaw is a game engine created by torus games and used for game boy editions of doom and duke nukem.