manifest.json

{
    "name": "CorgiOverflow", 
    "description": "Colorize StackOverflow (and add dog images)", 
    "version": "1.0.0", 
    "manifest_version": 3,
    "permissions": ["storage", "webNavigation", "declarativeContent", "tabs"],
    "content_scripts": [
        {
          "matches": [
            "https://stackoverflow.com/*"
          ],
          "css": [
            "styles.css"
          ]
        },
        {
          "matches": [
            "https://stackoverflow.com/*"
          ],
          "js": [
            "main.js"
          ]
        }
      ], 
    "action": {
        "default_popup": "popup.html", 
        "default_icon": {
            "16": "icon.png",
            "32": "icon.png",
            "48": "icon.png",
            "128": "icon.png"
          }
    }, 
    "options_page": "options.html"
}