Examine source code of select-spotify

{
  "manifest_version": 2,
  "name": "select-spotify",
  "version": "0.2.0",
  "icons": {
    "16": "assets/icons/favicon-16.png",
    "32": "assets/icons/favicon-32.png"
  },
  "description": "Allows song/album/playlist titles to be selected on Spotify web.",
  "homepage_url": "https://github.com/kholland950/select-spotify",
  "short_name": "select-spotify",
  "permissions": [
    "https://open.spotify.com/*"
  ],
  "content_security_policy": "script-src 'self'; object-src 'self'",
  "author": "Kevin Holland",
  "applications": {
    "gecko": {
      "id": "{B3AFB1AF-C33B-4856-B6A0-7786A8CA9D17}"
    }
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "assets/icons/favicon-16.png",
      "32": "assets/icons/favicon-32.png"
    },
    "default_title": "select-spotify",
    "browser_style": false
  },
  "options_ui": {
    "page": "options.html",
    "open_in_tab": true
  },
  "background": {
    "scripts": [
      "js/background.bundle.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "https://open.spotify.com/*"
      ],
      "js": [
        "js/contentScript.bundle.js"
      ]
    }
  ]
}