feat: Update extension to Manifest V3 for modern Chrome

[mbhutton]

I've updated the extension to be compatible with Manifest V3, preparing it for modern Chrome versions and future cross-browser support.

Changes include:

• Modified manifest.json:
  • Incremented manifest_version to 3.
  • Replaced background scripts with a service_worker.
• Refactored background.js:
  • Replaced deprecated chrome.tabs.getAllInWindow() with chrome.tabs.query().

The core tab de-duplication logic remains the same. The JavaScript APIs used are standard WebExtension APIs, promoting cross-platform compatibility.

Note: Manual testing in Chrome is required to confirm functionality after these changes.

[Copilot]

Pull Request Overview

This PR updates the Chrome extension to Manifest V3, replacing deprecated background scripting with a service worker and ensuring compatibility with modern Chrome and cross-browser environments.

• Bumped manifest_version to 3 and swapped background scripts for a service_worker in manifest.json
• Replaced chrome.tabs.getAllInWindow() with chrome.tabs.query() in background.js

Reviewed Changes

Copilot reviewed 1 out of 2 changed files in this pull request and generated 1 comment.

File	Description
manifest.json	Incremented to Manifest V3 and replaced background.scripts with service_worker
background.js	Swapped deprecated chrome.tabs.getAllInWindow for chrome.tabs.query callback

Files not reviewed (1)

• manifest.json: Language not supported

Comments suppressed due to low confidence (1)

background.js:4

• [nitpick] Since you're only looking for the first duplicate, consider using Array.prototype.find() or a for...of loop with break to short-circuit once a match is found and avoid unnecessary iterations.

tabs.forEach(function(otherTab) {