Add command-with-modifiers.js example (#1695)

* Adds TypeScript note and corrects a typo.

* Adds command-with-modifiers example. (redis#1688)

* Adds command-with-modifiers example. (redis#1688)

* Adds command-with-modifiers example. (redis#1688)

* Removed callbacks.

Co-authored-by: Simon Prickett <simon@redislabs.com>

Closes #1688.

examples/command-with-modifiers.js

@@ -0,0 +1,32 @@
+// Define a custom script that shows example of SET command
+// with several modifiers.
+
+import { createClient } from 'redis';
+
+async function commandWithModifiers() {
+  const client = createClient();
+
+  await client.connect();
+  await client.del('mykey');
+
+  let result = await client.set('mykey', 'myvalue', {
+      EX: 60,
+      GET: true
+    }
+  ); 
+  
+  console.log(result); //nil
+
+  result = await client.set('mykey', 'newvalue', {
+      EX: 60,
+      GET: true
+    }
+  );                        
+  
+  console.log(result); //myvalue
+
+  await client.quit();
+}
+
+commandWithModifiers();
+