Examine source code of Click2Highlight

{
  "manifest_version": 2,
  "name": "Click2Highlight",
  "version": "1.0",
  "description": "Double-click to toggle highlights on selected words for studying.",
  "permissions": [
    "activeTab",
    "storage"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "snippet.js"
      ]
    }
  ],
  "icons": {
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": "icons/icon48.png"
  },
  "author": "Robert Allen of ZingLab",
  "browser_specific_settings": {
    "gecko": {
      "id": "{79106ee3-a5c4-42f8-91a9-cfb43a553eda}"
    }
  }
}