propose a PR template to help newcomers get started more easily.

.github/pull_request_template.md

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+# Description
+
+Please include a summary of the changes and the related issue. Please also include relevant motivation and context. 
+
+Fixes # (issue)
+
+## Type of change
+
+Please delete options that are not relevant.
+
+- [ ] Bug fix (non-breaking change which fixes an issue)
+- [ ] New feature (non-breaking change which adds functionality)
+- [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
+- [ ] This change requires a documentation update
+
+# How Has This Been Tested?
+
+ Please also list any relevant details for your test configuration
+
+# Checklist:
+
+- [ ] I have run `bazel build @rules_rust//:rustfmt && ./rust_fmt.sh` to format my code
+- [ ] Updated documentation if needed
+- [ ] Tests added/amended
+- [ ] `bazel test //...`  passes locally
+- [ ] PR is contained in a single commit, using `git amend` see some [docs](https://www.atlassian.com/git/tutorials/rewriting-history)
+