Examine source code of Web Design Ruler

{
  "manifest_version": 3,
  "name": "Web Design Ruler",
  "version": "2.0.1",
  "description": "Essential design tools for web designers: pixel-perfect measurements, font identification, and professional color picking.",
  "browser_specific_settings": {
    "gecko": {
      "id": "webdesignruler@lxb-studio.com",
      "strict_min_version": "109.0"
    }
  },
  "icons": {
    "16": "assets/icons/icon16.png",
    "32": "assets/icons/icon32.png",
    "48": "assets/icons/icon48.png",
    "128": "assets/icons/icon128.png"
  },
  "action": {
    "default_popup": "popup/popup.html",
    "default_icon": {
      "16": "assets/icons/icon16.png",
      "32": "assets/icons/icon32.png",
      "48": "assets/icons/icon48.png",
      "128": "assets/icons/icon128.png"
    }
  },
  "permissions": [
    "activeTab",
    "storage",
    "contextMenus",
    "scripting",
    "clipboardWrite"
  ],
  "host_permissions": [
    "http://*/*",
    "https://*/*"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "http://*/*",
        "https://*/*"
      ],
      "js": [
        "scripts/content-script.js"
      ],
      "run_at": "document_end",
      "all_frames": false
    }
  ],
  "commands": {
    "_execute_action": {
      "suggested_key": {
        "default": "Ctrl+Shift+R",
        "mac": "Command+Shift+R"
      },
      "description": "Open Web Design Ruler"
    },
    "activate_eyedropper": {
      "suggested_key": {
        "default": "Ctrl+Shift+P",
        "mac": "Command+Shift+P"
      },
      "description": "Activate the Color Picker"
    }
  },
  "web_accessible_resources": [
    {
      "resources": [
        "scripts/content-script.js"
      ],
      "matches": [
        "http://*/*",
        "https://*/*"
      ]
    }
  ]
}