Examine source code of Change Case

{
  "manifest_version": 2,
  "name": "__MSG_extensionName__",
  "description": "__MSG_extensionDescription__",
  "version": "3.16",
  "default_locale": "en",
  "icons": {
    "64": "icon.svg",
    "128": "icon.svg"
  },
  "background": {
    "scripts": [
      "ep.js"
    ]
  },
  "permissions": [
    "contextMenus",
    "<all_urls>"
  ]
}