Examine source code of Apex Tools

{
  "manifest_version": 2,
  "name": "Apex Tools",
  "description": "Measure anything on the page with rulers, guides, snapping — plus a WhatFont-style font inspector and color eyedropper.",
  "version": "1.0.0",
  "author": "You",
  "browser_action": {
    "default_title": "Apex Tools",
    "default_popup": "popup/popup.html",
    "default_icon": "icons/icon.svg"
  },
  "background": {
    "scripts": [
      "background/background.js"
    ]
  },
  "permissions": [
    "activeTab",
    "tabs",
    "storage",
    "*://*/*"
  ],
  "icons": {
    "16": "icons/icon.svg",
    "32": "icons/icon.svg",
    "48": "icons/icon.svg",
    "128": "icons/icon.svg"
  },
  "commands": {
    "toggle-measure": {
      "suggested_key": {
        "default": "Alt+Shift+M"
      },
      "description": "Toggle measure overlay"
    },
    "clear-measures": {
      "suggested_key": {
        "default": "Alt+Shift+C"
      },
      "description": "Clear all measurements"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "info@waamtech.com"
    }
  },
  "web_accessible_resources": [
    "content/overlay.css",
    "icons/icon.svg"
  ]
}