Examine source code of Tweet Sig

{
  "manifest_version": 2,
  "name": "Tweet Sig",
  "version": "0.7resigned1",
  "description": "Post data in '#tweet-sig-in' or selection and put the posted url into '#tweet-sig-out' or clipboard.",
  "icons": {
    "48": "icons/tweet_sig_48.png"
  },
  "applications": {
    "gecko": {
      "id": "{2f26a5ff-a52f-4365-9677-5d9ef72bd40a}"
    }
  },
  "permissions": [
    "identity",
    "tabs",
    "contextMenus",
    "clipboardWrite",
    "storage"
  ],
  "background": {
    "persistent": false,
    "scripts": [
      "background.js"
    ]
  },
  "options_ui": {
    "page": "options.html"
  },
  "page_action": {
    "browser_style": false,
    "default_icon": "icons/tweet_sig_32.png",
    "default_title": "Tweet Sig"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "exclude_matches": [
        "https://twitter.com/intent/tweet*",
        "http://jrf.cocolog-nifty.com/archive/tweet_sig/fb_page_poster.html"
      ],
      "js": [
        "check_form.js"
      ]
    },
    {
      "matches": [
        "https://twitter.com/intent/tweet/complete?*"
      ],
      "js": [
        "clipboard.js",
        "check_comp.js"
      ]
    },
    {
      "matches": [
        "http://jrf.cocolog-nifty.com/archive/tweet_sig/fb_page_poster.html"
      ],
      "js": [
        "clipboard.js",
        "check_fbpp.js"
      ]
    }
  ]
}