docs: add the versioned documentation for v0.4.x

site/docusaurus.config.ts

@@ -93,6 +93,11 @@ const config: Config = {
               path: '/',
               banner: 'none'
             },
+            '0.4': {
+              label: '0.4',
+              path: '0.4',
+              banner: 'none'
+            },
             '0.3': {
               label: '0.3',
               path: '0.3',

site/src/components/HomepageFeatures/index.tsx

@@ -19,11 +19,11 @@ const FeatureList: FeatureItem[] = [
     ),
   },
   {
-    title: 'v0.3 Release now available',
+    title: 'v0.4 Release now available',
     image: require('@site/static/img/3.png').default,
     description: (
       <>
-        The v0.3 Release of Envoy AI Gateway is now available. See the <a href="/release-notes/v0.3">release notes</a> for more information.
+        The v0.4 Release of Envoy AI Gateway is now available. See the <a href="/release-notes/v0.4">release notes</a> for more information.
       </>
     ),
   },