WIP: add gemini-extension

[raybell-md]

Closes #100

I configured this as a gemini extension on my own machine as

{
  "name": "analytics-mcp",
  "version": "1.0.0",
  "description": "Google Analytics MCP Server for managing GA properties and accounts.",
  "mcpServers": {
    "analytics-mcp": {
      "command": "pipx",
      "args": [
        "run",
        "analytics-mcp"
      ],
      "env": {
        "GOOGLE_APPLICATION_CREDENTIALS": "XXXXXXXXXXX",
        "GOOGLE_PROJECT_ID": "XXXXXXXXXXX"
      }
    }
  }
}

I tried to look at https://github.com/gemini-cli-extensions/nanobanana to see how to include environmental variable injection when you install the extension.

Not tested but may help if someone on the teams wants to implement