Fix stream sample for consistency with v3.0.0 changes

[rolanday]

The updated readme sample for the 2.x to 3.x change has two issues:

1. Property accessor to stats object has been (appropriately) changed from stat to stats.

   const {path, stat: {size}} = entry; // wrong
   const {path, stats: {size}} = entry; // correct

2. Also, to get the stats object one. must now set the alwaysStat option to true as per the change log comments.

so, like this instead...

const readdirp = require('readdirp');
readdirp('.', {
  alwaysStat: true,
})
  .on('data', (entry) => {
    const {path, stats: {size}} = entry;
    console.log(`${JSON.stringify({path, size})}`);
  })
  // Optionally call stream.destroy() in `warn()` in order to abort and cause 'close' to be emitted
  .on('warn', error => console.error('non-fatal error', error))
  .on('error', error => console.error('fatal error', error))
  .on('end', () => console.log('done'));