Examine source code of Dimension

{
  "name": "Dimension",
  "version": "1.0",
  "description": "Giving you the window dimensions live!",
  "icons": {
    "16": "dimension_extensionicon_16.png",
    "48": "dimension_extensionicon_48_thicc.png",
    "128": "dimension_extensionicon_thicc.png"
  },
  "permissions": [
    "activeTab"
  ],
  "web_accessible_resources": [
    "dimension.*"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "css": [
        "dimension_extension.css"
      ],
      "js": [
        "dimension_extension.js"
      ]
    }
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "browser_action": {},
  "manifest_version": 2
}