add ScrollProgressBar component

[shubdev19]

What this PR does

Added a reusable ScrollProgressBar component that shows a thin
progress bar at the top of the page as the user scrolls down.

Changes made

• Added components/ScrollProgressBar.tsx
• Integrated it in pages/_app.tsx so it works on all pages

Tech used

• React hooks (useState, useEffect)
• TypeScript
• CSS-in-JS (inline styles)

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[melvincwng]

@shubsolos19 , thanks for the self-initiated/suggested feature enhancement to our community website.

Overall logic looks good, LGTM

Before I approve and merge the PR, please add yourself as a contributor in these 2 files:

1. contributors.tsx
2. CONTRIBUTORS.md

Tag/ping me once that's done

[melvincwng]

@shubsolos19, add yourself as a contributor here:

Make a new table row, each table row only has 6 cells - maintain the same consistency

1. https://github.com/yfosp/main-website/blob/main/community-website/pages/contributors.tsx
2. https://github.com/yfosp/main-website/blob/main/CONTRIBUTORS.md

[melvincwng]

Tag me once its done so I can approve and merge your request @melvincwng

[shubdev19]

@melvincwng Done! Added myself to both contributors.tsx and CONTRIBUTORS.md ✅

[melvincwng]

LGTM