Add a proper bibliography

[NeuroShepherd]

I see footnotes are currently being used for tagging the resources sited in the tutorial https://lmu-osc.github.io/FAIR-Data-Management/dmp.html#footnotes-1, but we should probably follow our own advice in the Introduction to Quarto tutorial.

(This can be an additional HiWi task.)

[NeuroShepherd]

Make use of the Quarto References feature too