feat (sponsors section): implement the sponsor section .

content/de/contribution.md

content/de/sponsors.md

content/en/sponsors.md

static/sponsors/logo_cosee.svg

static/sponsors/logo_deka.svg

static/sponsors/logo_h-da_eut.webp

static/sponsors/logo_uniberg.svg

static/sponsors/logo_uptime.svg

static/sponsors/logo_xynacom_black.png

themes/mainTheme/layouts/index.html

themes/mainTheme/layouts/partials/head.html

themes/mainTheme/layouts/partials/sponsors.html

themes/mainTheme/static/css/contribution.css

themes/mainTheme/static/css/sponsors.css