Enhance Source engine documentation with additional info

Added logo and related games to the Source engine entry.

Signed-off-by: Gabriel Lima Lopes <135924740+piratabrasileiro1@users.noreply.github.com>

Author: piratabrasileiro1

topics/source-engine/index.md

@@ -3,7 +3,10 @@ aliases: source-2013,source-sdk,source-1
 display_name: Source
 short_description: Source is game engine developed by valve software for half-life 2.
 topic: source-engine
+logo: source-engine.png
 wikipedia_url: https://en.wikipedia.org/wiki/Source_(game_engine)
+related: half-life-2,source-filmmaker,team-fortress-2,portal
 ---
 Source engine is a game engine published by valve software in 2004 and used for games like half-life 2.
 
+