Examine source code of 280 Twitter Counter

{
  "name": "__MSG_ext_name__",
  "short_name": "__MSG_ext_short_name__",
  "version": "3.0.1",
  "description": "__MSG_ext_description__",
  "homepage_url": "https://github.com/anein/twitter-count-characters",
  "author": "__MSG_ext_author__",
  "manifest_version": 2,
  "default_locale": "en",
  "icons": {
    "16": "img/favicon-16x16.png",
    "48": "img/favicon-48x48.png",
    "128": "img/favicon-128x128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://tweetdeck.twitter.com/*"
      ],
      "js": [
        "js/tweetdeck.js"
      ],
      "css": [
        "css/content.css"
      ],
      "run_at": "document_end"
    },
    {
      "matches": [
        "*://twitter.com/*"
      ],
      "js": [
        "js/web.js"
      ],
      "css": [
        "css/content.css"
      ],
      "run_at": "document_end"
    }
  ],
  "web_accessible_resources": [
    "js/scripts/web.js"
  ],
  "browser_action": {
    "default_title": "__MSG_ext_name__",
    "default_popup": "html/popup.html"
  },
  "permissions": [
    "storage",
    "tabs"
  ]
}