Support PHP EXIF extension

Problem / Motivation

I was recording a video to show someone how to set up geocoding from an image's EXIF data, and when I tried to show it working I got a screen with Error: Call to undefined function Drupal\geocoder_field\Geocoder\Provider\exif_imagetype() in Drupal\geocoder_field\Geocoder\Provider\File->geocodeQuery() (line 35 of modules/contrib/geocoder/modules/geocoder_field/src/Geocoder/Provider/File.php).

I'm assuming this is because exif_imagetype() isn't available in the global namespace because the Exif extension isn't installed. It would be neat if it was available.

Huge love for the service (:

Thanks!