To open index.html you will need live server.

Name: Live Server
Id: ritwickdey.LiveServer
Description: Launch a development local Server with live reload feature for static & dynamic pages
Version: 5.7.9
Publisher: Ritwick Dey
VS Marketplace Link: https://marketplace.visualstudio.com/items?itemName=ritwickdey.LiveServer

Install dependencies

to install go into root directory and enter following command in command prompt

npm install

To check eslint error

Run following command in root directory

npm run eslint