Added polish.xml with swap command_r with options_r

In Poland it is very common to alter the default keyboard mapping in MacOS by swapping the right command key with the right options key. [Popular polish blog post](http://www.makoweabc.pl/2013/07/polskie-znaki-w-os-x-za-pomoca-prawego-%E2%8C%98-zamiast-%E2%8C%A5/) that describes the Karabiner setup, attaching the changes that automate this setup.