Bumping chartjs to v3

[datenangebot]

This is the issue to discuss this comment at a common place. (I don't now if the discussion within the commit is a good place for it)

https://github.com/datenangebot/health/commit/c2267ce286d71849d907281b83964605bb8c1776#r89292092

@kenda Do you have some ressources to have a look at it? Otherwise I would try to go back to v2...