Add VisualD as first-class download

## turkeyman reported this on 2019-05-12T17:31:12Z

### Transfered from https://issues.dlang.org/show_bug.cgi?id=19866

### CC List

* johan_forsberg_86

### Description

On https://dlang.org/download.html

VisualD should have a direct download link with the Visual Studio icon next to it.