add Bit32 value for TiffBitsPerPixel

src/ImageSharp/Formats/Tiff/TiffBitsPerPixel.cs

@@ -70,6 +70,11 @@ public enum TiffBitsPerPixel
     /// </summary>
     Bit30 = 30,
 
+    /// <summary>
+    /// 32 bits per pixel. One byte for each color channel.
+    /// </summary>
+    Bit32 = 32,
+
     /// <summary>
     /// 36 bits per pixel. 12 bit for each color channel.
     ///