Add readme describing alternate stdlog config scenario

Author: Brian Lalor

README.md

@@ -128,6 +128,21 @@ stdLogger.Printf("[DEBUG] %+v", stdLogger)
 ... [DEBUG] my-app: &{mu:{state:0 sema:0} prefix: flag:0 out:0xc42000a0a0 buf:[]}
 ```
 
+Alternatively, you may configure the system-wide logger:
+
+```go
+// log the standard logger from 'import "log"'
+log.SetOutput(appLogger.Writer(&hclog.StandardLoggerOptions{InferLevels: true}))
+log.SetPrefix("")
+log.SetFlags(0)
+
+log.Printf("[DEBUG] %d", 42)
+```
+
+```text
+... [DEBUG] my-app: 42
+```
+
 Notice that if `appLogger` is initialized with the `INFO` log level _and_ you
 specify `InferLevels: true`, you will not see any output here. You must change
 `appLogger` to `DEBUG` to see output. See the docs for more information.