Show changed log2 fold change after shrinkage step

Highlight the change using a scatter plot where we expect low count values (1 vs 3 in raw counts) more than for higher ones (100 vs 300 in raw counts) using a MA-plot.

Add plot to:
https://biosustain.github.io/dsp_transcriptomics_training/log2-fold-change-shrinkage.html

similar to
https://biosustain.github.io/dsp_transcriptomics_training/ma-plot.html

Start by reading log2-fold-change-shrinkage.html and compare it with the existing ma-plot.html page. Add a MA-plot showing how shrinkage changes log2 fold changes, with the low-count and high-count examples described in the issue; the page should clearly highlight that difference.

Written by the indexing model from the issue text.