Examine source code of More Space Please

{
  "name": "More Space Please",
  "description": "add more spaces between characters, words and lines",
  "version": "0.0.1",
  "permissions": [
    "activeTab",
    "tabs",
    "storage"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_start"
    }
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_title": "Add spaces"
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": true
  },
  "icons": {
    "256": "icon/logo.png"
  },
  "manifest_version": 2,
  "browser_specific_settings": {
    "gecko": {
      "id": "{d3e0fac9-243c-4164-b2ea-ec463d0b874e}"
    }
  }
}