Website contains broken styling after 11ty upgrade

[haukesomm]

Current builds of the website contain styling issues such as an invisible sub-heading on the main page, missing card-header backgrounds and missing icon-backgrounds in the examples cards.

PR #898 implicitly updated 11ty to version 2.0.1 which is quite a big leap forward coming from a 0.x version. This might have broken a few things.

We should investigate this in order to restore the correct styling in the next version.