Localize other plugins

[1ec5]

This plugin could detect the presence of the mapbox-gl-directions and mapbox-gl-geocoder plugins and set their respective language options for consistency.

gl-geocoder’s language option is documented here: https://github.com/mapbox/mapbox-gl-geocoder/blob/53d06d871574a227a6b414f3370247ea16e29238/API.md#mapboxgeocoder

gl-directions’ language option appears to be unimplemented: mapbox/mapbox-gl-directions#129.

/cc @Kilatsat @lukasmartinelli