Examine source code of Image Size Info Plus

{
  "manifest_version": 2,
  "minimum_chrome_version": "100",
  "offline_enabled": true,
  "default_locale": "en",
  "name": "Image Size Info",
  "version": "3.0.1",
  "description": "Inserts option in the browser's image context menu to view image width, height and file size.",
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "options_page": "options.html",
  "icons": {
    "16": "images/icon_016.png",
    "32": "images/icon_032.png",
    "48": "images/icon_048.png",
    "64": "images/icon_064.png",
    "128": "images/icon_128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "run_at": "document_start",
      "js": [
        "includes/content.js"
      ],
      "all_frames": true
    }
  ],
  "permissions": [
    "contextMenus",
    "storage",
    "<all_urls>"
  ],
  "web_accessible_resources": [
    "images/icon_016.png",
    "images/icon_032.png",
    "images/icon_048.png",
    "images/icon_064.png",
    "images/icon_128.png",
    "includes/content.js",
    "options.html",
    "background.js"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{27c6c40a-1d7c-4bcf-91fa-7e10ba657809}"
    }
  }
}