docs: Add usage example of readline line-by-line parsing

[eljefedelrodeodeljefe]

While authoring a parser, I came across what you would normally get in organic search and found lots of it a little dangerous. Namely the use of big module APIs from npm don't occur to make the biggest sense here, since readline has a lot of good functionality built-in. Namely consuming file through readline's interface as steam.

In order to promote use of this, I'd suggest to add an example usage to the docs, which I derived from this stackoverflow link.

This case seemed really common to me, which is why I authored the below PR.

const readline = require('readline');
const fs = require('fs');

const rl = readline.createInterface({
  input: fs.createReadStream('sample.txt')
});

rl.on('line', function (line) {
  console.log('Line from file:', line);
});

PR: #4609

[silverwind]

Oh, this landed in 5a53cba!