Examine source code of WebsiteInjector

{
  "manifest_version": 2,
  "name": "WebsiteInjector",
  "description": "Simple extension to apply your styles and scripts on any web site.",
  "version": "1.1",
  "icons": {
    "512": "icon.svg"
  },
  "permissions": [
    "activeTab",
    "storage",
    "unlimitedStorage"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "*://*/*"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "browser_action": {
    "default_popup": "browserAction/popup.html",
    "default_title": "WebsiteInjector",
    "default_icon": "icon.svg",
    "theme_icons": [
      {
        "light": "light-icon.svg",
        "dark": "icon.svg",
        "size": 16
      },
      {
        "light": "light-icon.svg",
        "dark": "icon.svg",
        "size": 32
      }
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{7dfe3b1e-9a16-4dff-8c9e-a1caa91e00d7}"
    }
  }
}