Manifest version 2 is deprecated, and support will be removed in 2023. See https://developer.chrome.com/blog/mv2-transition/ for more details.

{
"manifest_version": 2,
"name": "ChatGPT Markdown Exporter",
"version": "1.0",
"description": "Export ChatGPT conversation to Markdown",
"permissions": ["activeTab", "cookies", "https://chat.openai.com/", "tabs"],
"content_scripts": [
{
"matches": ["https://chat.openai.com/chat/"],
"js": ["content_script.js"]
}
],
"background": {
"scripts": ["background_script.js"],
"persistent": false
},
"icons": {
"48": "icon48.png"
}
}