Examine source code of Reading Progress Memory

{
  "manifest_version": 2,
  "name": "Reading Progress Memory",
  "version": "1.0",
  "description": "Save how far you read automatically.",
  "permissions": [
    "storage",
    "tabs"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "icons": {
    "48": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{95a763cc-269e-4782-892f-ce16d3b4fca2}"
    }
  }
}