add MCP server badge

[punkpeye]

This PR adds a badge for the Vapi MCP Server server listing in Glama MCP server directory.

Glama performs regular codebase and documentation checks to:

• Confirm that the MCP server is working as expected
• Confirm that there are no obvious security issues with dependencies of the server
• Extract server characteristics such as tools, resources, prompts, and required parameters.

This badge helps your users to quickly assess that the MCP server is safe, server capabilities, and instructions for installing the server.

[punkpeye]

realized the project is missing a license

https://docs.github.com/en/communities/setting-up-your-project-for-healthy-contributions/adding-a-license-to-a-repository

Would you mind adding one?

We will automatically pick up the change (we scan every repo every 6 hours)