nginx-foodsharing.conf: pass rest api requests through index.php
A really straight forward "free" simplification.
Because we are using Symfony across the board now, we don't need a special PHP entry point for the REST API anymore - those requests can go directly through the index.php entry point now.
Once this is merged and deployed, we can directly delete restApi.php
in the main repository, with no further changes required :)
Related: #4