Add website skeleton

_config.yml

_config_reviewapps.yml

_data/helmholtz-centers.yml

_data/hifis_team.yml

_data/messengers.yml

_data/navigation.yml

_data/social_platforms.yml

_events/.gitkeep

_favicons/android-icon-144x144.png

_favicons/android-icon-192x192.png

_favicons/android-icon-36x36.png

_favicons/android-icon-48x48.png

_favicons/android-icon-72x72.png

_favicons/android-icon-96x96.png

_favicons/apple-icon-114x114.png

_favicons/apple-icon-120x120.png

_favicons/apple-icon-144x144.png

_favicons/apple-icon-152x152.png

_favicons/apple-icon-180x180.png

_favicons/apple-icon-57x57.png