Add CONTRIBUTING.md file (#2925)

Signed-off-by: Shlomo Heigh <shlomo.heigh@cyberark.com>

CONTRIBUTING.md

@@ -0,0 +1,6 @@
+# Contributing
+
+See the [Developer guide](docs/contributing/devguide.md) for information
+about setting up your development environment, and the
+[Contributing Process](docs/contributing/process.md) document
+for details about the workflow.