Note should be added in aliascnt doc about tagging code and `\newtheorem`

[mbertucci47]

The usual aliascnt trick for sibling theorems fails with the tagging code. This is because the new theorem block code does not use a traditional LaTeX counter (I'm pretty sure). It would be good to mention this in a note in the documentation since I'm fairly confident this is the most common usage of the package. It still works if amsthm is loaded since the amsthm firstaid still uses standard counters. See also latex3/tagging-project#229. Here's an example.

\DocumentMetadata
  {
    lang=en-US,
    pdfversion=2.0,
    pdfstandard=ua-2,
    tagging=on
  }
\documentclass{article}
\usepackage{aliascnt}

\newtheorem{foo}{Foo}% counter "foo"
\newaliascnt{baz}{foo}% alias counter "baz"
\newtheorem{baz}[baz]{Baz}
\aliascntresetthe{baz}

\begin{document}
  
\begin{foo}
abc
\end{foo}

\begin{baz}
blub
\end{baz}
\end{document}

[mbertucci47]

With the new block code, the example errors because alias counters are now supported by the kernel's own mechanism.