Add explanations to README.md file
This is a reroll of https://git.gfz-potsdam.de/dynamicexposure/globaldynamicexposure/exposure-japan/-/merge_requests/1 and https://git.gfz-potsdam.de/dynamicexposure/globaldynamicexposure/exposure-japan/-/merge_requests/2 to address issue #2 (closed)
Merge Requests shall be approved by others than the one who proposes them.