Allow designated initialization of struct

[f]

On Friday, 30 August 2024 at 16:03:27 UTC, ryuukk_ wrote:
> And in a perfect world:
>
> ```D
> my_fun( { c: 1 } );
> ```

this is perhaps c# syntax that allows ease of typing.

which is good to have for d to be modern language.

but the most urgent is perhaps coroutine,
it is only at first draft.

and we have 3 compiler that is not sharp enough. other language 
has only _ONE_ that great. IMHO