Temporary github PR template for sprint (pandas-dev#20055)

Author: jorisvandenbossche

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,3 +1,27 @@
+Checklist for the pandas documentation sprint (ignore this if you are doing
+an unrelated PR):
+
+- [ ] PR title is "DOC: update the <your-function-or-method> docstring"
+- [ ] The validation script passes: `scripts/validate_docstrings.py <your-function-or-method>`
+- [ ] The PEP8 style check passes: `git diff upstream/master -u -- "*.py" | flake8 --diff`
+- [ ] The html version looks good: `python doc/make.py --single <your-function-or-method>`
+- [ ] It has been proofread on language by another sprint participant
+
+Please include the output of the validation script below between the "```" ticks:
+
+```
+# paste output of "scripts/validate_docstrings.py <your-function-or-method>" here
+# between the "```" (remove this comment, but keep the "```")
+
+```
+
+If the validation script still gives errors, but you think there is a good reason
+to deviate in this case (and there are certainly such cases), please state this
+explicitly.
+
+
+Checklist for other PRs (remove this part if you are doing a PR for the pandas documentation sprint):
+
 - [ ] closes #xxxx
 - [ ] tests added / passed
 - [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`