Wrong type in `scanIterator` example

[MxKaras]

Description

Tiny point for y'all that tripped me up 🙃. On the latest version of the package, when I write

for await (const key of this.client.scanIterator({ MATCH: keyPattern })) {
    // ...
}

All available evidence shows that that key is string[]. This matches the scan iterator doc, but not what's in the main README:

for await (const key of client.scanIterator()) {
  // use the key!
  await client.get(key);
}

[nkaradzhov]

@MxKaras thanks for raising this, we will sort it out