Allow a custom fetch function to be provided in props

[tuukka]

I considered how to best customize the API requests and figured that allowing a custom fetch function would be the most flexible and clean way.

If this new prop isn't present, the library will continue to function as before.

For example, it becomes easy to modify the URL parameters:

  <ReactAutosuggestGeocoder
    fetch={(resource, options) => {
      return fetch(resource + "&key=value", options);
    }
    // ...
  />

[generalpiston]

@tuukka this is supposed to be integrated with pelias. Did you want to integrate this with something else?

[tuukka]

Hi @generalpiston! Yes and no: I have to send the requests to a Pelias instance which is behind a cloud API gateway that looks for the API key under a different parameter name. Also, I want to rewrite the autocomplete requests to go to the search endpoint as it works better in my use case.

Going forward, more tweaks may be needed especially as I don't control the instance.

[generalpiston]

Makes sense. Thanks!

[generalpiston]

@tuukka I'll see if I can do a release soon for this project.

[tuukka]

@generalpiston Thank you! I opened another pull request with some housekeeping in case it can help when making a release: #15