Reformat grml-tips

We present the grml-tips on our homepage: https://grml.org/tips/.

We implemented simple code highlighting in grml/grml.org#73 via grml/grml.org#83 but the visualization is not very pleasing.

We talked about reformatting grml-tips to improve the output.
`grml-tips` itself needs to cope with this new format and needs to be adjusted as well.

