Windows Resource Files and DUB

[Alexander via Digitalmars-d-learn]

There is a [Using Windows Resource Files with 
D2](https://wiki.dlang.org/Using_Windows_Resource_Files_with_D2) 
article, but it says nothing about DUB and is probably somewhat 
outdated.
So what actually works in `dub.json` (assuming the file 
`resource\my.res` exists):
```
{
  "dflags": ["-L/SUBSYSTEM:WINDOWS", "-Lresource\\my.res"]
}
```