Examine source code of Caption Catcher

{
  "manifest_version": 2,
  "name": "Caption Catcher",
  "version": "1.1",
  "description": "Automatically captures subtitle/caption files from video streaming sites",
  "permissions": [
    "webRequest",
    "storage",
    "downloads",
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "48": "icon.png"
    },
    "default_title": "Caption Catcher"
  },
  "icons": {
    "48": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "@caption-catcher",
      "strict_min_version": "58.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}