title: Is it possible to configure a Serilog Sub-logger from appSettings
body: <p>This is what I am doing now:</p>
  
  <pre><code>        Log.Logger = new LoggerConfiguration()
              .ReadFrom.AppSettings()
              .WriteTo.Logger(l =&gt; l.Filter.ByIncludingOnly(Matching.WithProperty("XXX")).WriteTo.File("output.txt"))
              .CreateLogger();
  </code></pre>
  
  <p>I have my main Logger set up in app.config, but I can't figure out the syntax for specifying a sub-logger there. I'd really like to avoid mixing code and appSettings configuration.</p>