Adding "Flutter for JetPack compose devs" to the sidenav (#11704)

As it says

---------

Co-authored-by: Parker Lougheed <[email protected]>

Author: sfshaza2

src/_data/sidenav.yml

@@ -34,6 +34,8 @@
       children:
         - title: Flutter for Android devs
           permalink: /get-started/flutter-for/android-devs
+        - title: Flutter for Jetpack Compose devs
+          permalink: /get-started/flutter-for/compose-devs
         - title: Flutter for SwiftUI devs
           permalink: /get-started/flutter-for/swiftui-devs
         - title: Flutter for UIKit devs