manifest.json

{
    "name": "Theme-this",
    "version": "1.0",
    "description": "Create your own custom theme or use some popular themes that go beyond the dark and light.",
    "permissions": ["activeTab", "declarativeContent", "storage", "tabs"],
    "background": {
      "scripts": ["background.js"],
      "persistent": false
    },
    "page_action": {
      "default_popup": "popup.html",
      "default_icon": {
        "16": "images/get_started16.png",
        "32": "images/get_started32.png",
        "48": "images/get_started48.png",
        "128": "images/get_started128.png"
      }
    },
    "icons": {
      "16": "images/get_started16.png",
      "32": "images/get_started32.png",
      "48": "images/get_started48.png",
      "128": "images/get_started128.png"
    },
    "content_scripts": [
      {
        "matches": [
          "https://www.google.com/", "<all_urls>"
        ],
        "js": ["scripts/apply.js"]
      }
    ],
    "manifest_version": 2
}