Examine source code of Page Keeper

{
  "manifest_version": 2,
  "name": "Page Keeper",
  "version": "1.1resigned1",
  "applications": {
    "gecko": {
      "id": "pagekeepeer@mudbile.com",
      "strict_min_version": "42.0"
    }
  },
  "description": "Manages (and generates) front pages for reddit.com without needing to log in",
  "icons": {
    "48": "icons/pagekeeper-48.png"
  },
  "permissions": [
    "activeTab",
    "tabs",
    "storage"
  ],
  "browser_action": {
    "default_icon": "icons/pagekeeper-48.png",
    "default_title": "Page Keeper",
    "default_popup": "popup/popup.html",
    "browser_style": false
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.reddit.com/*"
      ],
      "js": [
        "page_keeper.js"
      ]
    }
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  }
}