Merge: Update gitignore to exclude DS_Store

The .DS_Store file is automatically generated by the Mac OS filesystem to keep metainformation about that directory. This files is unnecessary to the project so should be excluded in the .gitignore

@privat

Pull-Request: #2060
Reviewed-by: Jean Privat <jean@pryen.org>
Reviewed-by: Alexis Laferrière <alexis.laf@xymus.net>
Reviewed-by: Lucas Bajolet <r4pass@hotmail.com>