docs: logging.getLogger('root') does not get you the root logger

[howardjones]

In the README, it says to use logging.getLogger('root') to initialise the root logger. That doesn't do that. That initialises a logger called "root".logging.getLogger(None) gets you the root logger.

(Just spent a while with logging_tree to figure out why I couldn't getting JSON logging working in non-main modules)

[bobbui]

will take a lôk

[bobbui]

updated docs thanks!