Add example plots to docs

Summary

This MR introduces the following changes

• adds a job to the CI pipeline which runs the example scripts in examples/plotting and hands the resulting plots as artifacts to the job which creates the docs
• updates in the docs, adding the above mentioned plots
• adds docs section for pt_vs_eff plot
• adds optional add_pt argument to dummy data
• fixing small bug in replace_placeholders_in_md.py which resulted in one line missing at the end

Relates to the following issues

• first step towards #159

The result is that we can add the output plot of an example script directly to the docs, which then also corresponds to the most recent version of the code.

Conformity

• Changelog entry
• [x] Documentation
• Development guidelines
• Style guides