Deployment: Dockerfile and Smithery config

[smithery]

This PR adds files for deploying your MCP server on Smithery. After deployment, users can use your server over WebSockets (hosted on Smithery) without needing to install any dependencies.

Changes

• Added Dockerfile to package your server for deployment.
• Added Smithery Configuration file to specify how to start your server. See documentation.
• Updated README to include popularity badge.

Server Details

• Smithery ID: @VapiAI/vapi-mcp-server
• Server Homepage: https://smithery.ai/server/@VapiAI/vapi-mcp-server

Action Items

• Build Passing: We verified that the Docker builds and your server starts up using an automated test.
• Code Review: Please review the changes to ensure the configuration is accurate for your server.