Make Reader class abstract

[mtar]

Describe the task. It can be a feature, documentation, etc.

Related: #1731

The Reader class in io_reader.py should not be instantiable. Also some docstrings are not descriptive.

Hedgedoc URL, if you are keeping notes, plots, logs in hedgedoc.

No response

Area

• datasets, data readers, data preparation and transfer
• model
• science
• infrastructure and engineering
• evaluation, export and visualization
• documentation

[mtar]

assign me

[github-actions]

Issue assigned to @mtar.