Examine source code of Active Reading

{
  "manifest_version": 2,
  "name": "Active Reading",
  "version": "1.0",
  "description": "Adds a simple checkmark tool to paragraphs upon clicking them while active",
  "icons": {
    "48": "icons/activeReading.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "activeReading.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{de393de1-6ae1-4e70-bd27-ab5de00b6ad9}"
    }
  }
}