Add Dev Proxy MCP server

[garrytrinder]

Example: https://github.com/microsoft/vscode-extension-samples/pull/1156/files

[garrytrinder]

While you're not able to publish extensions using the proposed API on the Marketplace, you can still share your extension with your peers by packaging and sharing your extension.

https://code.visualstudio.com/api/advanced-topics/using-proposed-api#sharing-extensions-using-the-proposed-api