[Enhancement] configure CORS headers

[woidda]

When working with different apps on local it would be nice to be able to set / configure CORS headers to be set for the nginx proxy.

In production for modern cloud apps the CORS headers can be dealt with on deployment configuration level, e.g. with Istio. With CORS headers set via the nginx proxy inside dory this would basically be the same behaviour.

I could not find an option inside /lib/dory/config.rb. Hence I am making this feature request and hope it is a no-brainer and that other people find that option usefull, too.