Polish translations

[tarnas14]

add Polish translations for all the stuff that is in the application ^^

any contribution is welcome, translations are in the i18n/index.js file, just add pl.translation object next to en and start translating whatever you want :)

if you want to provide translations for game components, follow the convention already established, e.g. with objectives you would copy export const en = and create export const pl = , translate it and use in 'i18n/index.js' in the pl.translation object