Examine source code of doppl

{
  "description": "Helps you break out of your echo chamber.",
  "manifest_version": 2,
  "name": "doppl",
  "version": "0.0.0.2",
  "homepage_url": "https://github.com/iancugniere/doppl",
  "icons": {
    "16": "images/icons/favicon-16.png",
    "48": "images/icons/favicon-48.png",
    "128": "images/icons/favicon-128.png"
  },
  "background": {
    "scripts": [
      "src/background.js"
    ]
  },
  "browser_action": {
    "default_icon": "images/icons/favicon-48.png",
    "default_popup": "src/popup/popup.html"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "src/content-scripts/main.js"
      ],
      "css": [
        "src/content-scripts/doppl-banner.css"
      ]
    }
  ],
  "permissions": [
    "activeTab",
    "https://newsapi.org/*",
    "https://fonts.googleapis.com/*",
    "https://api.airtable.com/v0/appCzMAJRnxG4KJI3/*"
  ]
}