keep headings remain in-view on toc scroll

[onweru]

Signed-off-by: weru fromweru@gmail.com

Closes #295

Changes / fixes

• A minor CSS scroll padding fix

Screenshots (if applicable)

(prefer animated gif)

Checklist

Ensure you have checked off the following before submitting your PR.

• [x] tested locally with the latest release of Hugo. This requirement is a standard
• [ ] added new dependencies
• [ ] updated the [docs]() ⚠️

[chipzoller]

Editing PR to use closing keywords.

[chipzoller]

Thanks!