Adds location manager which can be used to query the device's location (including permission and update handling)
Adds geoflutterfire to support uploading GPS coordinates alongside anchors and downloading anchors and objects by their location
Modifies cloud anchor example: Download button now queries and downloads all anchors along with the corresponding objects within a 100m radius of the device's current location
Bugfix: fixes bug on Android causing some examples to crash because the cloud anchor manager wasn't initialized