dmd foreach loops throw exceptions on invalid UTF sequences, use replacementDchar instead

[Alexey]

On Saturday, 6 November 2021 at 04:07:35 UTC, Alexey wrote:

> 3. IMHO, one grapheme should be and alias to ubyte[] or to one 
> BigInt;

or may be, even, define one grapheme as dchar[]. or maybe, even, 
define new separate type for 'codepoint' and define one grapheme 
as codepoint[].