feat(configuration): add thumbnail snap range setting

src/Eve-O-Preview/Configuration/Implementation/ThumbnailConfiguration.cs

@@ -93,6 +93,7 @@ namespace EveOPreview.Configuration.Implementation {
             this.ThumbnailMaximumSize = new Size(960, 540);
 
             this.EnableThumbnailSnap = true;
+            this.ThumbnailSnapRange = 20;
 
             this.ThumbnailZoomEnabled = false;
             this.ThumbnailZoomFactor = 2;
@@ -272,6 +273,7 @@ namespace EveOPreview.Configuration.Implementation {
         public Size ThumbnailMinimumSize { get; set; }
 
         public bool EnableThumbnailSnap { get; set; }
+        public int ThumbnailSnapRange { get; set; }
 
         [JsonProperty("EnableThumbnailZoom")]
         public bool ThumbnailZoomEnabled {