Examine source code of Universal Glitch Button

{
  "browser_action": {
    "default_icon": "icon.png",
    "default_title": "Glitch Project Info",
    "default_popup": "panel.html"
  },
  "id": "universal-glitch-button@glitch.com",
  "browser_specific_settings": {
    "gecko": {
      "id": "universal-glitch-button@glitch.com"
    }
  },
  "name": "Universal Glitch Button",
  "description": "View info about a glitch project",
  "homepage_url": "https://universal-glitch-button.glitch.me",
  "icons": {
    "16": "icon.png",
    "48": "icon.png",
    "128": "icon.png"
  },
  "permissions": [
    "tabs",
    "http://*/*",
    "https://*/*"
  ],
  "version": "3.5.0",
  "manifest_version": 2
}