Needed
manifest.json is required. It’s kinda like package.json in Node. manifest.json has info about your extensionmanifest.json file inside1{
2 "manifest_version": 2,
3 "name": "My Awesome Extension",
4 "description": "This extension is an awesome extension",
5 "version": "0.1",
6}
The icon right to your address bar is called a browser action. It is set as default_icon under browser_action. The size needs to be 19x19 pixels
1"browser_action": {
2 "default_icon": "icon_19.png"
3}
The icon that shows on the Extensions listing page is specified with 128 under icons. The size needs to be 128x128 pixels
1"icons": {
2 "128": "icon_128.png"
3 }