[Docs] Add demo video to introduction (#744)

Author: thisisgoldman

docs/introduction.mdx

@@ -43,6 +43,29 @@ Sequin works great for CDC use cases like:
 
 Sequin is a Docker image you can run next to your Postgres database. Sequin itself is built on Postgres and uses Postgres to store sink state.
 
+## Demo
+
+See Sequin in action. In this demo, we'll stream changes to Kafka, deploy to production, and scale to 2,000 messages / second.
+
+<div className="wistia_responsive_padding" style={{ padding: '56.88% 0 0 0', position: 'relative', marginBottom: '100px' }}>
+  <div className="wistia_responsive_wrapper" style={{ height: '100%', left: 0, position: 'absolute', top: 0, width: '100%', }}>
+    <iframe
+      src="https://fast.wistia.net/embed/iframe/hslcc4gnmv?seo=true&videoFoam=true"
+      title="Overview of Postgres streaming with Sequin Video"
+      allow="autoplay; fullscreen"
+      allowTransparency={true}
+      frameBorder="0"
+      scrolling="no"
+      className="wistia_embed"
+      name="wistia_embed"
+      msAllowFullScreen
+      style={{ width: '100%', height: '100%' }}
+    >
+    </iframe>
+  </div>
+</div>
+<script src="https://fast.wistia.net/assets/external/E-v1.js" async></script>
+
 ## Supported Sinks
 
 Sequin supports streaming to: