Add Jest Test Utility to sum all values in a given column

[Jean-Baptiste-Lasselle]

Just like in https://github.com/decoder-leco/decoderleco_deces_europe_reloaded/blob/feature/kr/decoderleco/deces_europe/jupyter/rewrite/notebooks/poc-eurostat-data-transformers.ipynb

It can be generalized to any dataframe, there's only to try catch the case when the column values are not numbers/Integers, there i can access / display each column types, @BorisTherin found how to do that