Update CONTRIBUTING.md

Add a hyperlink to enable people to more easily find beginner-friendly issues from the contributing markdown page.

Author: mfitz

CONTRIBUTING.md

@@ -35,6 +35,8 @@ information about the environment in which the process had been ran. It is also
 
 ## Contributing Code - Pull Request Process
 
+To find beginner-friendly issues that you might want to take a run at, look [here](https://github.com/arup-group/osmox/contribute).
+
 1. All new work is done in a branch taken from master, details can be found here:
 [feature branch workflow](https://www.atlassian.com/git/tutorials/comparing-workflows/feature-branch-workflow)
 2. Ensure your work is covered by unit tests to the required percentage level. This script 
@@ -54,4 +56,4 @@ do not have permission to do that, please request one of the reviewers to merge
 
 ## Attribution
 
-The Contribution Guide was adapted from [PurpleBooth's Template](https://gist.github.com/PurpleBooth/b24679402957c63ec426).
+The Contribution Guide was adapted from [PurpleBooth's Template](https://gist.github.com/PurpleBooth/b24679402957c63ec426).