replace gifs with videos

elections/migrations/0018_alter_electionshomepage_content.py

...static/styleguide2/images/background-images/bg-bartos.jpg

...ide2/images/background-images/bg-europarl-candidates.webp

...uide2/images/background-images/bg-flag-mobile-preview.jpg

...c/styleguide2/images/background-images/bg-flag-mobile.mp4

.../styleguide2/images/background-images/bg-flag-preview.jpg

...d/static/styleguide2/images/background-images/bg-flag.mp4

...tatic/styleguide2/images/background-images/bg-migrace.png

...plates/styleguide2/includes/molecules/menus/carousel.html