Add a package-support.json

[simonplend]

• https://github.com/nodejs/package-maintenance/blob/main/docs/PACKAGE-SUPPORT.md
• https://github.com/pkgjs/support

Potential package-support.json:

{
  "versions": [
    {
      "version": "*",
      "target": {
        "node": "supported"
      },
      "response": {
        "type": "best-effort"
      },
      "backing": {
        "none": ""
      }
    }
  ]
}

Add "support": true to package.json.