Add AI Background Remover to Image

[masakazuimai]

Following your note on #376, this is a fresh single-line PR for just one tool (not a bundle), and it doesn't duplicate an existing entry.

• AI Background Remover - Automatically detect the subject and remove image backgrounds with AI, entirely in the browser.

Meets CONTRIBUTING.md:

• Browser-based — AI runs fully client-side, no image is uploaded to a server
• Direct link — goes straight to the single tool (not a landing page)
• 100% free — no signup, trial, paywall, or usage limits

Placed in alphabetical order at the top of the Image section. Thanks for the earlier feedback!

[github-actions]

Hey masakazuimai! Thanks for your submission! 🚀

To keep awesome-devtools instantly accessible for everyone, all tools must be:

• Browser-based — no downloads or native app installs
• Direct link — goes straight to the tool (not a multi-tool landing page)
• 100% free — no signups, trials, paywalls, or usage limits

Please make sure your PR meets these criteria. It may take some time for your submission to be reviewed — you can occasionally comment with a "bump" to bring more attention to it.

Thanks for contributing! 🙌