Add build folders for simple game engine to .gitignore (#242)

Author: SaschaWillems

.gitignore

@@ -17,4 +17,16 @@ attachments/android/.idea
 attachments/android/.gradle/**
 attachments/android/app/.cxx/**
 attachments/android/app/build/**
-local.properties
+local.properties
+
+attachments/simple_engine/build/**
+attachments/simple_engine/Assets/**
+attachments/simple_engine/android/.gradle/**
+attachments/simple_engine/android/.idea
+attachments/simple_engine/android/.gradle/**
+attachments/simple_engine/android/app/.cxx/**
+attachments/simple_engine/android/app/build/**
+attachments/simple_engine/android/app/build/**
+attachments/simple_engine/android/gradle/wrapper/**
+attachments/simple_engine/android/gradlew
+attachments/simple_engine/android/gradlew.bat