Examine source code of Gentle Reminder

{
  "manifest_version": 2,
  "name": "Gentle Reminder",
  "version": "1.0",
  "description": "A gentle message from the better version of you when visiting distracting sites.",
  "permissions": [
    "tabs",
    "webNavigation",
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "web_accessible_resources": [
    "popup.css"
  ],
  "icons": {
    "48": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{6bc5e0fd-17b3-48ea-9af5-c96557f4015a}"
    }
  }
}