Add config flag to turn on debug logging

[blimmer]

You can pass enableLogging: true to the initialize call to get debug logging. This could be a useful feature.

enableLogging - Set to true to enable logging by default. Note that this will cause Appboy to log to the
javascript console, which is visible to all users! You should probably remove this or provide an alternate
logger with appboy.setLogger() before you release your page to production.

https://js.appboycdn.com/web-sdk/latest/doc/module-appboy.html#.initialize