DOC: update `pandas/core/ops.py` docstring template to accept examples
Checklist for the pandas documentation sprint

- [x] PR title is "DOC: update the <your-function-or-method> docstring"
- [x] The PEP8 style check passes: `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] It has been proofread on language by another sprint participant

The Chicago assigned docstrings uses a template with string formatting. To add examples for the various DataFrame operators, I modified the template to allow examples for each operator.

Opening this PR to get comments on this workflow.

I will work with all the ChiPy contributors to make sure we can get their examples in once we figure out the best way forward.