feat: add Dockerfile to use container as stdio mode

[bluzy]

Added Dockerfile to run MCP using docker.

docker build -t mcp-server-datahub:latest .

The image can be used by setup mcp.json like this:

{
  "servers": {
    "datahub": {
      "command": "docker",
      "args": [
        "run",
        "-i",
        "--rm",
        "-e",
        "DATAHUB_GMS_URL",
        "-e",
        "DATAHUB_GMS_TOKEN",
        "datahub-mcp-server:latest"
      ],
      "env": {
        "DATAHUB_GMS_URL": "http://localhost:8080",
        "DATAHUB_GMS_TOKEN": ""
      }
    }
  }
}

sse or http mode may be available after #29 merged.

docker run --rm \
-e DATAHUB_GMS_URL="http://localhost:8080" -e DATAHUB_GMS_TOKEN="" \
-e TRANSPORT=sse
datahub-mcp-server:latest