Examine source code of Clemail

{
  "manifest_version": 2,
  "name": "Clemail",
  "version": "1.0",
  "description": "Helps you keep your emails clear and concise. Reminds you that email is not always the best medium for a message.",
  "icons": {
    "48": "icons/icon.svg",
    "96": "icons/icon.svg"
  },
  "content_scripts": [
    {
      "matches": [
        "*://outlook.office.com/mail/*"
      ],
      "js": [
        "outlook-clemail.js"
      ]
    }
  ]
}