Examine source code of Save to Trello

{
  "name": "Save to Trello",
  "short_name": "To Trello",
  "description": "This firefox extension allows you to Create a Trello card from any webpage (including Gmail or other webmail) / Ideal for Inbox Zero. You can save the current page to Trello. When you find something in Firefox that you want to view later (email, article, ...), put it in your Trello board. It automatically syncs to your phone, tablet or computer so you can view it at any time.",
  "manifest_version": 2,
  "version": "1.2",
  "author": "Arnaud Lemercier",
  "developer": {
    "name": "Arnaud Lemercier",
    "url": "https://arnaud.lemercier.me"
  },
  "homepage_url": "https://wixiweb.fr",
  "icons": {
    "48": "icon.png",
    "96": "icon@x2.png"
  },
  "applications": {
    "gecko": {
      "id": "firefox-trello-add-card@wixiweb.fr"
    }
  },
  "page_action": {
    "browser_style": true,
    "default_icon": {
      "19": "action.svg",
      "38": "action.svg"
    },
    "default_title": "Save to Trello"
  },
  "permissions": [
    "tabs",
    "storage"
  ],
  "options_ui": {
    "page": "options.html",
    "browser_style": true
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  }
}