Keep Navigation bar stuck to the top even while scrolling

[sinharaksh1t]

Description

While scrolling the page, it'll be nice if the navigation bar sticks to the top. I have been constantly switching between light and dark theme based on the time of the day. If I'm at a problem somewhere in the latter half of the page, I have to scroll back to the top to toggle the theme and then scroll back down. This back and forth can be minimized by making the navigation bar stick to the top of the page.
Here is a pull request for the proposed fix: #332

I hope this feature can help others as well.

Screenshots

When at the top of the page

When not at the top of the page

[sinharaksh1t]

Pull request for the proposed fix: #332