feat: make the nav stick to the top of the pages

[MarwanBz]

• [*] Have you followed the [contributing guidelines] (https://github.com/github/opensource.guide/blob/HEAD/CONTRIBUTING.md)?yes
• [*] Have you explained what your changes do, and why they add value to the Guides?yes

Please note: we will close your PR without comment if you do not check the boxes above and provide ALL requested information.

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Enable Sticky Navigation Bar

Description:

This pull request introduces a sticky navigation bar to the Open Source Guide website. It implements the following:

• Fixed positioning for the navigation bar, ensuring it remains visible at the top of the screen while scrolling.
• This change improves user experience by providing easier access to navigation options throughout the website.

[jmeridth]

@MarwanBz could you please provide some screenshots? Thank you.

[MarwanBz]

Hey @jmeridth, yes sure
here is a video

sticky-nav.mp4

please check it out and let me what you think

[ahpook]

Hi, thanks for the pull request but I don't think this is a change we'll take.