add CONTRIBUTING

Author: xanhacks

CONTRIBUTING.md

@@ -0,0 +1,15 @@
+# How to contribute
+
+First of all, thank you for taking the time to contribute to this project.
+
+## Getting started
+
+Contributing to a project on [Github](https://github.com/xanhacks/ctf-docs) or [Gitlab](https://gitlab.com/xanhacks/ctf-docs) is pretty straight forward. If this is you're first time, these are the steps you should take.
+
+    Fork this repo.
+
+And that's it! Read the code available and change the part you don't like! You're change should not break the existing code and should pass the tests.
+
+If you're adding a new functionality, start from the branch master. It would be a better practice to create a new branch and work in there.
+
+When you're done, submit a pull request and for one of the maintainers to check it out. We would let you know if there is any problem or any changes that should be considered.