Create CONTRIBUTING.md

.github/CONTRIBUTING.md

+### Issue Templates
+If you are reporting an issue, you need to replace the parts of the template where you see `{{some text}}`.
+
+### Code Structure
+Repository = Data layer = Reads and writes data from a location (variable/DB/external API/etc).
+
+Service = Business layer = Operates on data and transforms data from a given structure to a required structure.