Examine source code of Rickroll_Avoider

{
  "manifest_version": 2,
  "name": "Rickroll_Avoider",
  "version": "1.0",
  "description": "Highlights rickrolls on a webpage",
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "main.js"
      ]
    }
  ]
}