Updated contributing.md

Provided a hint for syncing an old fork

docs/collections/_development/contributing.md

@@ -22,3 +22,8 @@ How to submit a pull request:
 Every time a commit is pushed to the master branch, [Travis CI](https://travis-ci.org/) will be triggered to perform the build. It will use [abapmerge](https://github.com/larshp/abapmerge) to merge all the includes into a single file, the build can be downloaded from [https://raw.githubusercontent.com/abapGit/build/master/zabapgit.abap](https://raw.githubusercontent.com/abapGit/build/master/zabapgit.abap)
 
 Alternatively, use the GitHub webinterface to change the files and submit a pull request.
+
+
+If you already have an old fork and would like to create a new pull request, 
+you can sync your old fork to current state following this guide: 
+https://github.com/KirstieJane/STEMMRoleModels/wiki/Syncing-your-fork-to-the-original-repository-via-the-browser