Slack Message Checker

manifest.json

{
  "update_url": "https://clients2.google.com/service/update2/crx",
  "manifest_version": 2,
  "name": "Slack Message Checker",
  "description": "This extension checks your message and shows an alert before sending in Slack.",
  "version": "1.0.0",
  "content_scripts": [
    {
      "matches": [
        "https://*.slack.com/*"
      ],
      "css": [
        "css/contents.css"
      ],
      "js": [
        "js/jquery-2.1.4.min.js",
        "js/contents.js"
      ],
      "run_at": "document_end"
    }
  ],
  "options_page": "options.html",
  "content_security_policy": "script-src 'self' 'unsafe-eval'; object-src 'self'",
  "permissions": [
    "storage"
  ]
}