Ensure speech-dispatcher recommendations are in the installer

In a real situation, those packages are installed by the chain of
depends/recommends orca -> speech-dispatcher ->
(speech-dispatcher-espeak-ng, sound-icons).

However that chain is broken, in all likelyhood by debian-cd dependency
handling, cf. #601203.

This mention should ensure these packages are present in the generated
ISO.

Fixes: #46

simple-cdd/profiles/offline.downloads

@@ -14,3 +14,6 @@ unrar
 # Ensure pipewire-pulse is available so that when wireplumber gets
 # installed it can pull it as a recommends
 pipewire-pulse
+# Ensure speech-dispatcher recommends are available
+sound-icons
+speech-dispatcher-espeak-ng