some docs

Co-authored-by: Guy Royse <guy@guyroyse.com>

docs/scan-iterators.md

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+# Scan Iterators
+
+> :warning: The scan iterators API in v5 has breaking changes from the previous version. For more details, refer to the [v4-to-v5 guide](./v4-to-v5.md#scan-iterators).
+
+[`SCAN`](https://redis.io/commands/scan) results can be looped over using [async iterators](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol/asyncIterator):
+
+```typescript
+for await (const keys of client.scanIterator()) {
+  const values = await client.mGet(keys);
+}
+```
+
+This works with `HSCAN`, `SSCAN`, and `ZSCAN` too:
+
+```typescript
+for await (const entries of client.hScanIterator('hash')) {}
+for await (const members of client.sScanIterator('set')) {}
+for await (const membersWithScores of client.zScanIterator('sorted-set')) {}
+```
+
+You can override the default options by providing a configuration object:
+
+```typescript
+client.scanIterator({
+  TYPE: 'string', // `SCAN` only
+  MATCH: 'patter*',
+  COUNT: 100
+});
+```