Add tunisian data to datasets

[doneachh]

Describe the feature you'd like to see

Add tunisian data to:

growth_factors_cagr.csv
efficiency_gains_cagr.csv
fuel_shares.csv
district_heating.csv

[doneachh]

Hi @hazemakhalek ! :)
since you have researched the data for Morocco, I thought it might be a good idea to tag you here. A colleague and I have researched this data for Tunisia and I am considering adding these entries to the model. However, there are a few lines where there is simply no data in Tunisia. Was this also the case for Morocco and how did you deal with it or how did you research the data for Morocco?

TUN_PyPSA-Earth__154.xlsx