Examine source code of HTTP Headers Customize

{
  "manifest_version": 2,
  "name": "HTTP Headers Customize",
  "version": "1.0.3resigned1",
  "description": "'HTTP Headers Customize' extension rewrite http headers based on a rules.",
  "icons": {
    "48": "icons/icon-off-48.svg"
  },
  "developer": {
    "name": "fumidzuki",
    "url": "https://github.com/fumidzuki/http-headers-customize"
  },
  "background": {
    "scripts": [
      "js/background.js"
    ]
  },
  "options_ui": {
    "page": "options.html",
    "open_in_tab": true
  },
  "browser_action": {
    "browser_style": true,
    "default_title": "HTTP Headers Customize",
    "default_popup": "popup.html"
  },
  "permissions": [
    "storage",
    "webRequest",
    "webRequestBlocking",
    "<all_urls>"
  ],
  "content_security_policy": "script-src 'self'; object-src 'self';",
  "browser_specific_settings": {
    "gecko": {
      "id": "{9a25dc0c-4775-422c-9c01-b6af1eddeeb0}"
    }
  }
}