Examine source code of Blue Light Filter

{
  "manifest_version": 2,
  "name": "Blue Light Filter",
  "version": "1.0",
  "description": "Reduces blue light after 20:00 to protect your eyes.",
  "permissions": [
    "storage",
    "activeTab"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "browser_action": {
    "default_popup": "popup/popup.html",
    "default_icon": "icon.png"
  },
  "options_ui": {
    "page": "options/options.html",
    "open_in_tab": false
  },
  "icons": {
    "48": "icon.png"
  },
  "applications": {
    "gecko": {
      "id": "blue-light-filter@namkks.com"
    }
  }
}