Merge pull request #1497 from Unity-Technologies/add-docs

Add doc to link to PRTools process [skip ci]

Author: ashwinimurt

docs/update_mono_in_unity.md

@@ -0,0 +1,7 @@
+# Update Mono in Unity
+
+[PRTools](https://github.cds.internal.unity3d.com/unity/prtools) is used to update Mono build.zips in [Unity](https://github.cds.internal.unity3d.com/unity/unity).
+
+Updates must be run using the [PRTools Yamato Project](https://yamato.cds.internal.unity3d.com/jobs/842-prtools).
+
+Please refer to [Update Mono in Unity](https://github.cds.internal.unity3d.com/unity/prtools/blob/master/README.md).