Draft: Add viscosity profiles to data/viscosityProfiles directory

Viscosity profile files in .json format as background viscosity for simulation runs with temperature dependent viscosity are stored in /data/terraneo/viscosityProfiles/. Two profiles are provided (ViscosityProfile_Stotz_et_al_2017.json and ViscosityProfile_Colli_et_al_2022.json). The README.md file will contain a detailed description of the two profiles and additional references for a profound knowledge about the viscosity profiles.