docs: redirect users to the correct page from header button (#6779)

docs/src/components/Header/Desktop.tsx

@@ -39,6 +39,22 @@ type Props = {
   className?: string;
 };
 
+const NewLookButton = () => {
+  const currentUrl = typeof window !== 'undefined' ? window.location.href : 'https://cube.dev/docs';
+  const nextUrl = currentUrl.replace('cube.dev/docs', 'cube.dev/docs-next');
+
+  return (
+    <Button
+      href={nextUrl}
+      target="_blank"
+      className={styles.headerButton}
+    >
+      <Icon style={{ fontSize: '22px' }} type="bulb" />
+      Try out the new look!
+    </Button>
+  );
+}
+
 const Header: React.FC<Props> = (props) => (
   <Layout.Header className={props.className}>
     <div className={styles.searchDimmer}></div>
@@ -58,14 +74,7 @@ const Header: React.FC<Props> = (props) => (
           {/*  Community*/}
           {/*</Button>*/}
 
-          <Button
-            href="https://cube.dev/docs-next"
-            target="_blank"
-            className={styles.headerButton}
-          >
-            <Icon style={{ fontSize: '22px' }} type="bulb" />
-            Try out the new look!
-          </Button>
+          <NewLookButton />
 
           <Button
             href="https://slack.cube.dev/"