Added message to exception to show which asset failed (#297)

In reference to #190 the error message is not clear about which asset it tried to load, this simply adds that to the error message
[release]

src/WebOptimizer.Core/Asset.cs

@@ -130,7 +130,7 @@ public static IEnumerable<string> ExpandGlobs(IAsset asset, IWebHostEnvironment
 
                 if (files.Count == 0)
                 {
-                    throw new FileNotFoundException($"No files found matching exist in an asset");
+                    throw new FileNotFoundException($"No files found matching exist in an asset {asset}");
                 }
 
                 asset.Items[PhysicalFilesKey] = files;