Examine source code of Twitter Required Alt Text

{
  "name": "Twitter Required Alt Text",
  "version": "1.2",
  "icons": {
    "72": "icon-72x72.png",
    "96": "icon-96x96.png",
    "128": "icon-128x128.png",
    "512": "icon-512x512.png"
  },
  "description": "Small extension that will force you to add alt text to images when tweeting",
  "content_scripts": [
    {
      "matches": [
        "https://*.twitter.com/*",
        "http://*.twitter.com/*"
      ],
      "js": [
        "script.js"
      ]
    }
  ],
  "manifest_version": 2
}