COM interface must inherit from IUnknown example has a regular D interface

## Richard (Rikki) Andrew Cattermole reported this on 2022-08-30T18:41:04Z

### Transferred from https://issues.dlang.org/show_bug.cgi?id=23316

### Description

````markdown
The COM interfaces example is a little deceiving.

It shows a regular D interface in use, but not a COM interface.

https://dlang.org/spec/interface.html#com-interfaces
````