Examine source code of Save Button

{
  "manifest_version": 2,
  "name": "Save Button",
  "description": "Save bookmarks, quotes, and images with Save Button",
  "version": "1.2.19",
  "icons": {
    "16": "/icon/icon-16.png",
    "32": "/icon/icon-32.png",
    "48": "/icon/icon-48.png",
    "96": "/icon/icon-96.png",
    "128": "/icon/icon-128.png"
  },
  "author": "lofi.mx",
  "homepage_url": "https://savebutton.com",
  "permissions": [
    "activeTab",
    "tabs",
    "contextMenus",
    "storage",
    "alarms",
    "<all_urls>"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "org.savebutton@savebutton.org",
      "strict_min_version": "91.0"
    }
  },
  "background": {
    "persistent": false,
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_icon": {
      "16": "/icon/icon-grey-16.png",
      "32": "/icon/icon-grey-32.png",
      "48": "/icon/icon-grey-48.png",
      "96": "/icon/icon-grey-96.png"
    },
    "default_popup": "popup.html"
  },
  "options_ui": {
    "open_in_tab": false,
    "page": "options.html"
  }
}