Examine source code of slack-redir

{
  "manifest_version": 2,
  "name": "slack-redir",
  "description": "Rplaces the slack-redir.net links in Slack with direct links",
  "author": "Vladimir Borisov",
  "icons": {
    "64": "slack-redir-64.png",
    "128": "slack-redir-128.png"
  },
  "version": "1.3",
  "content_scripts": [
    {
      "matches": [
        "https://*.slack.com/*"
      ],
      "js": [
        "main.js"
      ]
    }
  ]
}