Add spatial audio support

Source/LibationFileManager/Configuration.HelpText.cs

@@ -82,6 +82,13 @@ namespace LibationFileManager
                 from the decrypted audiobook. This does not require
                 re-encoding.
                 """ },
+            {nameof(SpatialAudioCodec), """
+                The Dolby Digital Plus (E-AC-3) codec is more widely
+                supported than the AC-4 codec, but E-AC-3 files are
+                much larger than AC-4 files.
+
+                AC-4 cannot be converted to MP3.
+                """ },
         }
         .AsReadOnly();