* add Pro Git book and Git section in Azerbaijani and Bulgarian languages
* add Pro Git book and Git section for Greek and Dutch/Netherlands languages
* add Slovenian language for books; add Pro Git book and Git section to Slovenian language books
* add authors for Pro Git book for Azerbaijani and Bulgarian languages
* fix md formatting errors for books languages az and sl
* fix new line in the end of file for books languages az and sl
* fix md lint formatting error - not enough empty lines after section for books languages az and sl
* fix md linter error in books az file
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Co-authored-by: Roman Lazunin <roman.lazunin@xylem.com>