add examples

[andrewharvey]

https://github.com/mapbox/mapbox-gl-geocoder/tree/master/example feels more like a debug page to aid development rather than examples of how to implement mapbox-gl-geocoder.

I think we should rename it to debug, and maintain separate examples without all the extra code in the current example related to live reloading. Specifically I'd like an example for:

• basic usage https://www.mapbox.com/mapbox-gl-js/example/mapbox-gl-geocoder/
• using localGeocoder to accept lat/lon coordinates https://github.com/mapbox/mapbox-gl-geocoder/blob/master/example/index.js#L26
• using filter to limit results to an admin region from the Mapbox Geocoding API https://github.com/mapbox/mapbox-gl-geocoder/blob/master/example/filter.js#L29
• search box outside the map Attach controls to arbitrary DOM nodes mapbox-gl-js#3685 (comment) add example to use any element as the geocoder input #137
• keep map in sync with geocoder proximity Proximity updates based on map movement #118 (comment)

I think these examples should sit with the mapbox-gl-js examples as all infrastructure exists already and it's easier for users to find examples for the whole Mapbox GL JS ecosystem when are in one place.

[andrewharvey]

• part 1 to be addressed in add extra mapbox-gl-geocoder examples mapbox-gl-js#5915
• part 2 to be addressed by point to external docs and rename examples directory as debug #139