Make some classes internal

src/ImageSharp/Formats/Heif/HeifItem.cs

@@ -6,7 +6,7 @@ namespace SixLabors.ImageSharp.Formats.Heif;
 /// <summary>
 /// Provides definition for a HEIF Item.
 /// </summary>
-public class HeifItem(Heif4CharCode type, uint id)
+internal class HeifItem(Heif4CharCode type, uint id)
 {
     /// <summary>
     /// Gets the ID of this Item.

src/ImageSharp/Formats/Heif/HeifItemLink.cs

@@ -6,7 +6,7 @@ namespace SixLabors.ImageSharp.Formats.Heif;
 /// <summary>
 /// Link between <see cref="HeifItem"/> instances within the same HEIF file.
 /// </summary>
-public class HeifItemLink(Heif4CharCode type, uint sourceId)
+internal class HeifItemLink(Heif4CharCode type, uint sourceId)
 {
     /// <summary>
     /// Gets the type of link.

src/ImageSharp/Formats/Heif/HeifLocation.cs

@@ -6,7 +6,7 @@ namespace SixLabors.ImageSharp.Formats.Heif;
 /// <summary>
 /// Location within the file of an <see cref="HeifItem"/>.
 /// </summary>
-public class HeifLocation(long offset, long length)
+internal class HeifLocation(long offset, long length)
 {
     /// <summary>
     /// Gets the file offset of this location.