Use Modern JS

[harshkhandeparkar]

Since we are thinking of dropping node 10 support in #1935 and because most browsers support ES6 and beyond, we can:

• Remove all vars and use let/const instead.
• Use async/await and promises.
• Even use ES6 imports by converting normal JS files to .mjs. (which will be compiled by browserify into a single package)
• Output ESM for NodeJS instead of commonjs.
• Worker Threads (NodeJS Only)

ref: https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c

This can be done file by file without issues. Anything else?

[Bl4ck-h00d]

Hi! I would like to work on this.

[saurabhmehta1601]

Please assign me this issue . I would really like to work on it .