Add plots for ehrdata

[Zethson]

Description of feature

• Check whether our existing plots that we got from scanpy even make sense for 3D EHRData
• Vibe code a few plots using ehrdata.blobs and discuss them with us on zulip
• Add new (vibe coded) matplotlib plots that adhere to our current API

An example is #232

[eroell]

• Longitudinal behaviour of a continuous variable for different individuals from previous work here