docs: add inspect.software health badge

[Nayjest]

This PR adds the inspect.software health badge to the README.

Why this PR?
Your project ranks in the upper rating bands of our open-source health index (which measures maintainability, responsiveness, and security). This badge makes that standing objectively visible to your users. Our index is a free public good, and scores cannot be bought.

Technical details:

• No tracking: Static SVG served via GitHub's CDN. No JavaScript, no third-party tracking.
• No maintenance: The badge updates automatically after every inspection.
• Transparent: Links directly to your full report, based on our open methodology.

If you prefer to keep your README minimal, feel free to close this PR without replying. Your report will remain publicly available and up-to-date either way.

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}