Add BlurHash support to backend

MediaBrowser.Controller/Entities/BaseItem.cs

@@ -2222,6 +2222,7 @@ namespace MediaBrowser.Controller.Entities
                 existingImage.DateModified = image.DateModified;
                 existingImage.Width = image.Width;
                 existingImage.Height = image.Height;
+                existingImage.Hash = image.Hash;
             }
             else
             {

MediaBrowser.Controller/Entities/ItemImageInfo.cs

@@ -28,6 +28,12 @@ namespace MediaBrowser.Controller.Entities
 
         public int Height { get; set; }
 
+        /// <summary>
+        /// Gets or sets the blurhash.
+        /// </summary>
+        /// <value>The blurhash.</value>
+        public string Hash { get; set; }
+
         [JsonIgnore]
         public bool IsLocalFile => Path == null || !Path.StartsWith("http", StringComparison.OrdinalIgnoreCase);
     }