Added the CONTRIBUTORS file to the project.

CONTRIBUTORS

@@ -0,0 +1,14 @@
+For the purpose of tracking copyright, this is the list of individuals and
+organizations who have contributed source code to this Swift package.
+
+For employees of an organization/company where the copyright of work done
+by employees of that company is held by the company itself, only the company
+needs to be listed here.
+
+## COPYRIGHT HOLDERS
+
+- Röck+Cöde VoF. (all contributors with '@rock-n-code.com')
+
+## PROJECT AUTHORS
+
+- Javier Cicchelli <javier@rock-n-code.com>