Work/hugo merged
- Move completely to Hugo and use new CSS;
- Correct some JS logic (still 1 left), use vanilla JS, and remove redundant stuff;
- Make all strings on the UI translatable. Translators can add names for credit, they will be put in a meta tag;
- There are 2 PO files created for translation now. By default, a language with both these 2 files translated at least 50% will be added;
- Transfer most of translation-related works to po4a, the Python script now only makes some changes related to the
LANGUAGE_NAME
entry and the language selection bar; - Include commits of the upstream's master branch.