ghostty: add missing GStreamer dependencies

Ghostty 1.2.0 added the ability to play audio snippets when encountering
a bell character (BEL) using GStreamer. Before this commit, however,
GStreamer was never listed as a direct dependency, though it was working
for the majority of users, as it was still included as a transitive
dependency from GTK 4 itself, except for one user who managed to crash
Ghostty by trying to play MP3 audio while not having the "good" GStreamer
plugins installed *anywhere* within their system, since only base and bad
plugins are installed by default with GTK 4, and by extension, Ghostty.

See ghostty-org/ghostty#11720 for the initial report.

pkgs/by-name/gh/ghostty/package.nix

@@ -9,6 +9,7 @@
   freetype,
   glib,
   glslang,
+  gst_all_1,
   gtk4-layer-shell,
   harfbuzz,
   libadwaita,
@@ -75,6 +76,9 @@ stdenv.mkDerivation (finalAttrs: {
     libadwaita
     libx11
     gtk4-layer-shell
+    gst_all_1.gstreamer # Used for playing audio, e.g. audible bells
+    gst_all_1.gst-plugins-good
+    gst_all_1.gst-plugins-base
 
     # OpenGL renderer
     glslang