Add new category "Voxel Engine"

ISSUE_TEMPLATE

@@ -33,6 +33,7 @@ Thanks for contributing! Tutorial in this list should provide a guided path for
 * [ ] Shell
 * [ ] Template Engine
 * [ ] Visual Recognition System
+* [ ] Voxel Engine
 * [ ] Web Search Engine
 * [ ] Web Server
 * [ ] Uncategorized