Add stream examples. (#1830)

* Adds stream consumer and producer scripts to doc.

* Updated build command example.

* Adds stream producer example.

* Adds basic stream consumer example.

* Added isolated execution.

* Update README.md

* Update stream-consumer.js

Co-authored-by: Leibale Eidelman <leibale1998@gmail.com>

examples/stream-consumer.js

@@ -0,0 +1,65 @@
+// A sample stream consumer using the blocking variant of XREAD.
+// This consumes entries from a stream created by stream-producer.js
+
+import { createClient, commandOptions } from 'redis';
+
+async function streamConsumer() {
+  const client = createClient();
+
+  await client.connect();
+
+  let currentId = '0-0'; // Start at lowest possible stream ID
+
+  while (true) {
+    try {
+      let response = await client.xRead(
+        commandOptions({
+          isolated: true
+        }), [
+          // XREAD can read from multiple streams, starting at a 
+          // different ID for each...
+          {
+            key: 'mystream',
+            id: currentId
+          }
+        ], {
+          // Read 1 entry at a time, block for 5 seconds if there are none.
+          COUNT: 1,
+          BLOCK: 5000
+        }
+      );
+
+      if (response) {
+        // Response is an array of streams, each containing an array of
+        // entries:
+        // [
+        //   { 
+        //     "name": "mystream",
+        //     "messages": [
+        //       {
+        //         "id": "1642088708425-0",
+        //         "message": {
+        //           "num": "999"
+        //         }
+        //       }
+        //     ]
+        //   }
+        // ]
+        console.log(JSON.stringify(response));
+
+        // Get the ID of the first (only) entry returned.
+        currentId = response[0].messages[0].id;
+        console.log(currentId);  
+      } else {
+        // Response is null, we have read everything that is 
+        // in the stream right now...
+        console.log('No new stream entries.');
+      }
+    }
+  } catch (err) {
+    console.error(err);
+  }
+}
+
+streamConsumer();
+