Examine source code of Better UI

{
  "name": "Better UI",
  "version": "0.0.4",
  "manifest_version": 3,
  "description": "A browser extension for Edge and Chrome to make websites look more readable and user-friendly.",
  "action": {
    "default_popup": "./popup.html"
  },
  "content_scripts": [
    {
      "matches": [
        "https://*/*",
        "http://*/*"
      ],
      "allFrames": true,
      "js": [
        "./main.js"
      ]
    },
    {
      "matches": [
        "https://*.github.com/*"
      ],
      "css": [
        "./styles/github.css"
      ]
    },
    {
      "matches": [
        "https://*.duckduckgo.com/*"
      ],
      "css": [
        "./styles/duckduckgo.css"
      ]
    },
    {
      "matches": [
        "https://*.youtube.com/*"
      ],
      "css": [
        "./styles/youtube.css"
      ]
    },
    {
      "matches": [
        "https://*.bing.com/search*"
      ],
      "css": [
        "./styles/bing.css"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "betterui@enigmalabs.site"
    }
  }
}