chore: Update documentation with regards to logging (#260)

Author: wooj2

README.md

@@ -150,9 +150,12 @@ Try some other calls?  Help us better understand what you think the most critica
 ## Logging
 The AWS SDK for Swift uses SwiftLog for high performant logging.  Many of our calls are issued to the `debug` level of output, which are disabled in the console by default.  To see debug output to your console, you can add the following code to your application in a place where you know that the code will be called once and only once:
 ```swift
-LoggingSystem.bootstrap { label in
-    var handler = StreamLogHandler.standardOutput(label: label)
-    handler.logLevel = Logger.Level.debug
-    return handler
-}
+SDKLoggingSystem.initialize(logLevel: .debug)
+```
+
+Alternatively, if you need finer grain control of instances of SwiftLog, you can call `SDKLoggingSystem.add` to control specific instances of the log handler.  For example:
+```swift
+SDKLoggingSystem.add(logHandlerFactory: S3ClientLogHandlerFactory(logLevel: .debug))
+SDKLoggingSystem.add(logHandlerFactory: CRTClientEngineLogHandlerFactory(logLevel: .info))
+SDKLoggingSystem.initialize()
 ```