Improve README with popup screenshot and usage GIF

[alex-w-developer]

Problem

The README explains what GetBlocked! does, but it does not currently show the extension visually.

Adding screenshots would help new users and contributors quickly understand:

• what the popup looks like
• how the extension appears when used on a real site
• what kind of local privacy report the extension provides

Proposed fix

Update the README with visual examples of the extension.

Add:

1. A screenshot of the GetBlocked! popup.
2. A short GIF showing the extension being used on a normal website.

The GIF could show:

• loading a website
• opening the GetBlocked! popup
• seeing blocked trackers / cleaned links / detected categories update

Files likely involved

• README.md
• assets/
• Optional: docs/

Suggested asset names

assets/popup-screenshot.png
assets/usage-demo.gif

Acceptance criteria

• README includes a screenshot of the extension popup.
• README includes a GIF showing the extension being used on a site.
• Images are stored in the repository, preferably under assets/.
• Screenshot and GIF do not reveal private browsing data, accounts, emails, cookies, or personal information.
• The README remains clean, beginner-friendly, and not too large.
• Image file sizes are kept reasonable so the repository does not become unnecessarily heavy.