This also renames the category of the diagrams post in order to be in
line with the other tutorials.

- Use image overlays for the cards
- Use mix-blend-mode to make contrast high enough
- Show post image if one is defined

- Use default font instead of Hermann
- Reduce size by removing the image and some metainformation

This does not implement multilanguage support for the whole website, but
only for the content of specific pages.

- Only display the three most recent news entries on mobile
- Create an improved default image for news with default title images

- Redesign news cards
- Reduce border-radius

- Introduce a new card style
- Prepare all the other cards to be more generalized