DUB: How to link an external library on Windows 10?

[Ki Rill via Digitalmars-d-learn]

I have a Raylib project on Windows using DUB. I've added raylib-d 
via `dub add`. But what I can't figure out is how to tell DUB to 
link against raylib library.

I have the following project structure:
```
-> source
---> app.d
-> libraylib.a
-> raylib.dll
-> etc...
```
I'd like to use either .a or .dll. Do you have any ideas?