Add VS Code for the Web badge to README (#2871)

* Initial plan

* Add VS Code for the Web badge to README

Co-authored-by: spboyer <7681382+spboyer@users.noreply.github.com>

* Fix URL encoding in VS Code for the Web badge to use + instead of %20

Co-authored-by: spboyer <7681382+spboyer@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: spboyer <7681382+spboyer@users.noreply.github.com>

Author: Copilot

README.md

@@ -25,6 +25,7 @@ This solution's backend is written in Python. There are also [**JavaScript**](ht
 
 [![Open in GitHub Codespaces](https://img.shields.io/static/v1?style=for-the-badge&label=GitHub+Codespaces&message=Open&color=brightgreen&logo=github)](https://github.com/codespaces/new?hide_repo_select=true&ref=main&repo=599293758&machine=standardLinux32gb&devcontainer_path=.devcontainer%2Fdevcontainer.json&location=WestUs2)
 [![Open in Dev Containers](https://img.shields.io/static/v1?style=for-the-badge&label=Dev%20Containers&message=Open&color=blue&logo=visualstudiocode)](https://vscode.dev/redirect?url=vscode://ms-vscode-remote.remote-containers/cloneInVolume?url=https://github.com/azure-samples/azure-search-openai-demo)
+[![Open in VS Code for the Web](https://img.shields.io/static/v1?style=for-the-badge&label=VS+Code+for+the+Web&message=Open&color=purple&logo=visualstudiocode)](https://vscode.dev/azure?azdTemplateUrl=https://github.com/azure-samples/azure-search-openai-demo)
 
 ## Important Security Notice