[Cocos Studio Manual] Add "2. how-to-create-game" Korean Version

- Add "2.1 new game project" korean version
- Add "2.2 Add game assets" korean version
- Add "2.2.1 New File" korean version
- Add "2.2.2 Adjust Resolution" korean version
- Add "2.2.3 Reuse Scene" korean version
- Add "2.2.4 Import" korean version
- Add "2.2.5 SpriteSheet" korean version
- Update related link