Improve slightly misleading comment for beginners (#916)

The comment about how to override the LogLevel in appsettings.json did not make it clear that the required keys must appear within `Logging` in appsettings.json.

src/Microsoft.ApplicationInsights.AspNetCore/Extensions/ApplicationInsightsExtensions.cs

@@ -227,11 +227,16 @@
                         // The default behavior is to capture only logs above Warning level from all categories.
                         // This can achieved with this code level filter -> loggingBuilder.AddFilter<Microsoft.Extensions.Logging.ApplicationInsights.ApplicationInsightsLoggerProvider>("",LogLevel.Warning);
                         // However, this will make it impossible to override this behavior from Configuration like below using appsettings.json:
+                        // {
+                        //   "Logging": {
                         //     "ApplicationInsights": {
                         //       "LogLevel": {
                         //         "": "Error"
                         //       }
+                        //     }
                         //   },
+                        //   ...
+                        // }
                         // The reason is as both rules will match the filter, the last one added wins.
                         // To ensure that the default filter is in the beginning of filter rules, so that user override from Configuration will always win,
                         // we add code filter rule to the 0th position as below.