Examine source code of Alfs Buttons

{
  "manifest_version": 2,
  "name": "Alfs Buttons",
  "version": "1.1resigned1",
  "description": "Only add a button to identify the current Youtube/Vimeo url and let be detected for load in sidebar",
  "icons": {
    "48": "icon.svg"
  },
  "applications": {
    "gecko": {
      "id": "alfs-b@thepante.github.io"
    }
  },
  "permissions": [
    "tabs",
    "activeTab"
  ],
  "page_action": {
    "browser_style": true,
    "default_icon": "icon-pip.svg",
    "default_title": "Watch in sidebar"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  }
}