add doom related topics

topics/goldsrc/index.md

@@ -0,0 +1,7 @@
+---
+display_name: Goldsrc
+short_description: GoldSource is a game engine created by Valve Corporation, based on the original Quake engine.
+topic: goldsrc
+wikipedia_url: https://en.wikipedia.org/wiki/Goldsrc
+---
+GoldSource is a 1998 game engine created by Valve Corporation, based on the original Quake engine used by half-life 1.

topics/id-tech/index.md

@@ -0,0 +1,7 @@
+---
+display_name: Id Tech
+short_description: Id Tech is a game engine developed by id Software in 1993.
+topic: id-tech
+wikipedia_url: https://en.wikipedia.org/wiki/Id_Tech
+---
+Id Tech is a game engine developed by id Software in 1993, known for running games such as Doom, Hexen, and Quake.

topics/quakec/index.md

@@ -0,0 +1,7 @@
+---
+display_name: Quakec
+short_description: Quakec is a programming language created by John Carmack.
+topic: quakec
+wikipedia_url: https://en.wikipedia.org/wiki/Quakec
+---
+Quakec is a 1996 programming language created exclusively for the game Quake, by John Carmack.

zscript/index.md

@@ -0,0 +1,6 @@
+---
+display_name: Zscript
+short_description: Zscript is a programming language created in 2005 by the Zdoom team.
+topic: zscript 
+---
+Zscript is a programming language created in 2005 by the Zdoom team for gzdoom and used in their games/mods.