White list prerequisite needed in GTM plugin doc

[BobAchgill]

Thanks a million for writing the plugin!

One suggestion...

It took me a long time to realize why i was not getting the GTM plugin to work. It would be helpful that you say somewhere in the setup documenting that the config.xml has to have this whitelist statement

<!-- Don't block any requests -->
<access origin="*" />

otherwise the GTM plugin is blocked from sending data out.

All Cordova doc strongly recommends NOT using that line so i had removed it not knowing it was a prerequisite for the GTM plugin!

Bob Achgill