Add https://docs.ultralytics.com/help/contributing (#11460)

* Add https://docs.ultralytics.com/help/contributing

* Add https://docs.ultralytics.com/help/contributing

.github/ISSUE_TEMPLATE/bug-report.yml

@@ -80,6 +80,6 @@ body:
       label: Are you willing to submit a PR?
       description: >
         (Optional) We encourage you to submit a [Pull Request](https://github.com/ultralytics/yolov5/pulls) (PR) to help improve YOLOv5 for everyone, especially if you have a good understanding of how to implement a fix or feature.
-        See the YOLOv5 [Contributing Guide](https://github.com/ultralytics/yolov5/blob/master/CONTRIBUTING.md) to get started.
+        See the YOLOv5 [Contributing Guide](https://docs.ultralytics.com/help/contributing) to get started.
       options:
         - label: Yes I'd like to help by submitting a PR!