add build-engine related topics

Author: piratabrasileiro1

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: build, build-engine, build2, duke-nukem-engine, con-script, con-files
+wikipedia_url: https://en.wikipedia.org/wiki/Build_(game_engine)
+---
+The Build Engine is a 2.5D game engine created by Ken Silverman, best known for powering Duke Nukem 3D and several other shooters from 1990.

topics/serious-engine/index.md

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+---
+display_name: Serious Engine
+short_description: Serious Engine is a game engine created by croteam for serious sam games.
+topic: serious-engine
+wikipedia_url: 
+---
+Serious Engine is a 2001 game engine created by croteam and published by devolver digital used for serious sam games.