Add Italian to Localization Plugin `MapLocale` class

We support `name_it` in Mapbox Streets v8.3.

Seen in Mapbox Studio

The Localization Plugin's `MapLocale` class could stand to have Italian added to it for convenient access/usage.

https://github.com/mapbox/mapbox-plugins-android/blob/master/plugin-localization/src/main/java/com/mapbox/mapboxsdk/plugins/localization/MapLocale.java#L110-L111

Reference pr is https://github.com/mapbox/mapbox-plugins-android/pull/575 where Japanese and Korean were added to the plugin.

cc as simple fyi @1ec5 @jcsg

Start in plugin-localization/src/main/java/com/mapbox/mapboxsdk/plugins/localization/MapLocale.java at the referenced lines, and compare the Japanese and Korean additions in pull request 575. Confirm that Italian is exposed through MapLocale for the supported name_it value and run the plugin's existing checks to verify the change.

Written by the indexing model from the issue text.