MNT: Add PR template

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,29 @@
+## Checklist for submitter
+
+- [ ] I am submitting a new CEP: [Put your title here](#link-to-markdown-preview-in-branch).
+  - [ ] I am using the CEP template by creating a copy `cep-0000.md` named `cep-????.md` in the root level.
+- [ ] I am submitting modifications to CEP XX. <!-- reflect CEP number here -->
+- [ ] Something else: (add your description here).
+
+<!-- delete section below if this is not a new CEP -->
+## Checklist for CEP approvals
+
+- [ ] The vote period has ended and the vote has passed the necessary quorum and approval thresholds.
+- [ ] A new CEP number has been minted. Usually, this is `${greatest-number-in-main} + 1`.
+- [ ] The `cep-????.md` file has been renamed accordingly.
+- [ ] The `# CEP XX - ` header has been edited accordingly.
+- [ ] The CEP status in the table has been changed to approved.
+- [ ] The last modification date in the table has been updated accordingly.
+- [ ] The `pre-commit` checks are passing.
+
+
+<!-- Just as a reminder, everyone in all conda org spaces (including PRs)
+     must follow the Conda Org Code of Conduct (link below).
+
+     Finally, once again, thanks for your time and effort. If you have any
+     feedback in regards to your experience contributing here, please
+     let us know!
+
+     Helpful links:
+       - Conda Org COC: https://github.com/conda/governance/blob/main/CODE_OF_CONDUCT.md
+-->