Examine source code of Baseball Savant Button

{
  "manifest_version": 3,
  "name": "Baseball Savant Button",
  "version": "1.51",
  "description": "Adds Baseball Savant buttons next to player names on fantasy sites.",
  "permissions": [
    "storage",
    "tabs",
    "scripting"
  ],
  "host_permissions": [
    "https://*.espn.com/*",
    "https://fantasy.espn.com/*",
    "https://www.cbssports.com/*",
    "https://baseball.fantasysports.yahoo.com/*",
    "https://sports.yahoo.com/*",
    "https://nfc.shgn.com/*",
    "https://ottoneu.fangraphs.com/*",
    "https://underdogfantasy.com/*",
    "https://www.fantrax.com/*"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "action": {
    "default_popup": "popup/popup.html",
    "default_icon": {
      "16": "icons/icon16.png",
      "48": "icons/icon48.png",
      "128": "icons/icon128.png"
    }
  },
  "icons": {
    "16": "icons/icon16.png",
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "savant-extension@example.com",
      "strict_min_version": "109.0"
    }
  }
}