Examine source code of ffclock

{
  "manifest_version": 2,
  "name": "Clock",
  "version": "2.0",
  "description": "Clean and Simple",
  "author": "Jovan Lanik",
  "homepage_url": "https://github.com/jovanlanik",
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_title": "Clock"
  },
  "applications": {
    "gecko": {
      "id": "clean@simple.clock",
      "strict_min_version": "60.0"
    }
  }
}