docs: update sector.csv

doc/configtables/sector.csv

@@ -23,10 +23,9 @@ district_heating,--,,`prepare_sector_network.py <https://github.com/PyPSA/pypsa-
 -- -- heat_exchanger_pinch_point_temperature_difference,K,float,Heat pump pinch point temperature difference in heat exchangers assumed for approximation.
 -- -- isentropic_compressor_efficiency,--,float,Isentropic efficiency of heat pump compressor assumed for approximation. Must be between 0 and 1.
 -- -- heat_loss,--,float,Heat pump heat loss assumed for approximation. Must be between 0 and 1.
--- fraunhofer_heat_utilisation_potentials,--,Dictionary with names of heat sources for which data by Fraunhofer ISI (Manz et al. 2024) should be used,
+-- heat_utilisation_potentials,--,Dictionary with names of heat sources for which data by Fraunhofer ISI (`Manz et al. 2024 <https://www.sciencedirect.com/science/article/pii/S0960148124001769>) should be used,
 -- -- geothermal,-,Name of the heat source. Must be the same as in ``heat_pump_sources``,
-
--- -- -- key,-,string used to complete URL for data download,
+-- -- -- key,-,string used to complete URL for data download - e.g. `geothermal_65` or `geothermal_85`","i.e file names in `Fordatis <https://fordatis.fraunhofer.de/handle/fordatis/341.3?mode=simple>`,
 -- -- -- constant_temperature_celsius,°C,heat source temperature,
 -- -- -- column_name,-,name of the data column in retrieved GeoDataFrame,