Examine source code of LinkSteam

{
  "name": "LinkSteam",
  "version": "1.0",
  "description": "Opens steam links whenever chrome opens any kind of steam link such as store.steampowered.com/*",
  "icons": {
    "16": "/icons/link-steam-16.png",
    "32": "/icons/link-steam-32.png",
    "64": "/icons/link-steam-64.png",
    "128": "/icons/link-steam-128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "https://store.steampowered.com/*"
      ],
      "js": [
        "main.js"
      ]
    }
  ],
  "manifest_version": 2
}