Link to readme anchor does not scroll to the right heading

Summary

As discussed on https://gitlab.slack.com/archives/CETG54GQ0/p1582122905474600

A link to a readme anchor does not scroll you to the right heading. For example, https://gitlab.com/gitlab-org/slack-notifier/#custom-http-client should load the page then scroll to Custom HTTP Client but it doesn’t, just stays on the very top.

Steps to reproduce

• Go to https://gitlab.com/gitlab-org/slack-notifier/#custom-http-client
• Observe that the page does not scroll to Custom HTTP Client, just stays at the top.

What is the current bug behavior?

Page does not scroll to the right heading.

What is the expected correct behavior?

Page should scroll to the right heading.

Output of checks

This bug happens on GitLab.com