Added CONTRIBUTING.md

* Pointing out that development and contribution must be done on linaro
* Asking not to submit pull requests on github
* Resolves MLCE-774

Change-Id: Ifbcf4a7ab8e714b5c77425f0e4174520e0ece09f
Signed-off-by: Pablo Marquez Tello <pablo.tello@arm.com>
Reviewed-on: https://review.mlplatform.org/c/ml/ComputeLibrary/+/7946
Benchmark: Arm Jenkins <bsgcomp@arm.com>
Tested-by: Arm Jenkins <bsgcomp@arm.com>
Reviewed-by: Gunes Bayir <gunes.bayir@arm.com>
Comments-Addressed: Arm Jenkins <bsgcomp@arm.com>
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
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index 0000000..171d101
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+Please read https://arm-software.github.io/ComputeLibrary/latest/contribution_guidelines.xhtml
+
+Here on github we only publish a snapshot of the main development branch for each release, that's the reason why we don't accept pull requests.
+
+Please submit your patch for review to review.mlplatform.org.
+
+The development is structured in the following way:
+
+    Release repository: https://github.com/arm-software/ComputeLibrary
+    Development repository: https://review.mlplatform.org/#/admin/projects/ml/ComputeLibrary
+    Please report issues here: https://github.com/ARM-software/ComputeLibrary/issues