docs: add winget install instructions and badge

[AThraen]

Summary

• Adds `winget install UmageAI.CodeShellManager` as the recommended install path in the README.
• Adds a winget version badge next to the existing GitHub Release / Build / License badges.

Notes

• Until the manifest is merged into microsoft/winget-pkgs the badge will render as "no version found" — which is expected and self-resolves once Microsoft accepts the PR (typically within ~24h after their bot validates).

🤖 Generated with Claude Code

[AThraen]

@copilot can we also add a prominent link back to umage.ai and our product page for this? https://umage.ai/products/code-shell-manager/ in the top of the main readme and perhaps also if there is another place in github where we can pin a link?

[Copilot]

@copilot can we also add a prominent link back to umage.ai and our product page for this? https://umage.ai/products/code-shell-manager/ in the top of the main readme and perhaps also if there is anoth...

Done in c56814d — added a prominent blockquote callout right below the badges:

🌐 umage.ai/products/code-shell-manager — product page, screenshots, and latest news

For pinning on GitHub itself, you can also set the product page URL as the repository's Website field — go to the repo → click the ⚙️ gear icon next to About (top-right of the repo page) → paste https://umage.ai/products/code-shell-manager/ into the Website field. That surfaces it prominently on the repo homepage for anyone who lands there.