Location header for new resource

[siegfried]

As The response SHOULD include a Location header identifying the location of the newly created resource is mentioned in JSON-API specification, I wonder if the location header should be put in JaResource.Create.created.

https://github.com/vt-elixir/ja_resource/blob/master/lib/ja_resource/create.ex#L93

[psteininger]

@siegfried I have taken over maintenance of this project. Is this feature something still important to you (3 years later)? Would you want to take stab at PR?