formatting, small changes

.clang-format

.gitignore

meson.build

po/POTFILES

po/de.po

po/flashcards.pot

resources/flashcards.gresource.xml

resources/meson.build

resources/ui/create-card.blp

resources/ui/create-category.blp

resources/ui/flashcards.gresource.xml

resources/ui/meson.build

resources/ui/window.blp

src/create-category.c

src/create-category.h

src/database.c

src/database.h

src/flashcardsapp.c

src/flashcardsapp.h

src/flashcardsappwin.c