Examine source code of Echo Navigation

{
  "manifest_version": 2,
  "name": "Echo Navigation",
  "version": "5.0.2",
  "description": "highlight reader with keyboard shortcuts",
  "browser_specific_settings": {
    "gecko": {
      "id": "echo-navigation-e247beb3@firefox.extension",
      "strict_min_version": "101.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "permissions": [
    "tabs",
    "storage",
    "unlimitedStorage",
    "<all_urls>",
    "bookmarks",
    "history",
    "sessions"
  ],
  "browser_action": {
    "default_icon": {
      "16": "icons/icon-16.png",
      "48": "icons/icon-48.png",
      "64": "icons/icon-64.png",
      "128": "icons/icon-128.png"
    },
    "default_title": "Echo Navigation",
    "default_popup": "popup/popup.html"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "icons": {
    "16": "icons/icon-16.png",
    "48": "icons/icon-48.png",
    "64": "icons/icon-64.png",
    "128": "icons/icon-128.png"
  }
}