Check pl (Polskie) locale and fix typos

Check locales by native and fix typos.

Project use [jekyll-multiple-languages-plugin](https://github.com/kurtsson/jekyll-multiple-languages-plugin). Each locale file are keeped in `_18n` folder.
For example `en` is located in `_18n/en.yml` file.

Project was translated by translation service not by human. So it can keep typos.

Need to check current issue language.

- Fork
- Create branch 181_pl_locale
- Commit and create PR

Start by opening the Polish locale file in the `_18n` directory, following the example path `_18n/en.yml`. Review the current Polish translations for typos and commit the corrections on the requested `181_pl_locale` branch. Done means the Polish locale has been checked and a pull request is created.

Written by the indexing model from the issue text.