fill in basic details for remaining processors/modules

src/content/docs/modules/nats/client.md

@@ -4,8 +4,18 @@ sidebar:
     label: Client
     order: 1
 ---
-
+This module connects to a [NATS](https://nats.io/) server and subscribes to a subject.
 - **type**: `nats.client`
 - **params**:
-    - **url**
-    - **subject**
+    - **url**: the URL of the NATS server to connect to (e.g. `nats://localhost:4222`)
+    - **subject**: the subject to subscribe to
+
+### Example
+Connect to a local NATS server and subscribe to the `events` subject 
+```
+- id: natsClient
+  type: nats.client
+  params:
+    url: nats://localhost:4222
+    subject: events
+```