Add XML comments to public entities.

Aaru.Images/GDI/GDI.cs

@@ -41,6 +41,9 @@ namespace Aaru.DiscImages
 {
     // TODO: There seems no be no clear definition on how to treat pregaps that are not included in the file, so this is just appending it to start of track
     // TODO: This format doesn't support to specify pregaps that are included in the file (like Redump ones)
+    /// <summary>
+    /// Implements reading Dreamcast GDI disc images
+    /// </summary>
     public sealed partial class Gdi : IOpticalMediaImage
     {
         ulong        _densitySeparationSectors;