Project spatial-fertilization-excretions additional "source" and "output" folders

Support to the code estimating nutrient (N, P, K) fertilization and human excretions at fine resolution scale in France, hosted on the Github repository https://github.com/Thomas-Starck/spatial-fertilization-excretions The "source" and "output" folder were not uploaded on Github because of the large size of the files they contain. The source folder is needed for the code to run; the output folder contains the detailed results. See instructions in the README file on the Github repository to execute the code reproduce results. The results can also be seen in a user-friendly website on https://thomas-starck.github.io/spatial-fertilization-excretions/