Dev doc line highlighting

[huayunh]

Describe the bug / expected behavior

The line highlighting in dev doc is at it again. Area being highlighted in dev doc is mismatching the part that's supposed to be highlighted.

What are the steps to reproduce?

1. Go to dev branch of the dev doc. https://brightlayer-ui-components.github.io/angular-dev/components/three-liner/examples
2. Scroll to the bottom of the three liner examples page
3. Observe that the highlighted area is not the same as the part we intend to highlight.
4. Now do the same to the master branch. Everything looks fine. https://brightlayer-ui-components.github.io/angular/components/three-liner/examples

Screenshots

Dev Branch

Master Branch

Anything else to add?

Discovered during #629