Ionic 2 safely store api key in config.xml

I have an Ionic application that is using the cordova google maps plugin.

In my config.xml I have

<plugin name="cordova-plugin-googlemaps" spec="^2.1.1">
    <variable name="API_KEY_FOR_IOS" value=“$AFLKSDJFSD" />
    <variable name="LOCATION_WHEN_IN_USE_DESCRIPTION" value="Show your location on the map" />
    <variable name="LOCATION_ALWAYS_USAGE_DESCRIPTION" value="Trace your location on the map" />

I assume, but could be wrong that it is not secure to store the api key in the config.xml

Is there a best practice for storing sensitive variables in config.xml

I have seen this thread but I am still unsure how to use the supplied code in config.xml