Created PR template for the rccl repo (#1118)

[ROCm/rccl commit: 8f471ba537]

projects/rccl/.github/PULL_REQUEST_TEMPLATE.md

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+## Details
+___Do not mention proprietary info or link to internal work items in this PR.___
+
+**Work item:** _"Internal", or link to GitHub issue (if applicable)._
+
+**What were the changes?**  
+_One sentence describing the work done._
+
+**Why were the changes made?**  
+_Explain the motivation behind the work. Provide any publicly-available historical context._
+
+**How was the outcome achieved?**  
+_Technical details behind the work. Explain any publicly-available hardware peculiarities._
+
+**Additional Documentation:**  
+_What else should the reviewer know?_
+
+## Approval Checklist
+___Do not approve until these items are satisfied.___
+- [ ] Verify the CHANGELOG has been updated, if
+  - there are any NCCL API version changes,
+  - any changes impact library users, and/or
+  - any changes impact any other ROCm library.