Lib: Update readme with info on logging

Author: mdtusz

README.md

@@ -25,6 +25,11 @@ chart types, including 3D charts, statistical graphs, and SVG maps.
 
 ## Quick start options
 
+**It is important to note that logging is turned off by default in v1.13.0 onwards.**
+To turn logging on for development, you will want to run
+`Plotly.setPlotConfig({ logging: 2 })` before any plotting.
+See [this file](https://github.com/plotly/plotly.js/blob/master/src/lib/loggers.js) for more details.
+
 #### Download the latest release
 [Latest Release on Github](https://github.com/plotly/plotly.js/releases/)