Indentation of `--xmp` output

[muzimuzhi]

--xmp outputs are surrounded by <XMP> ... </XMP>, thus logically have nesting level 1. But currently (in v1.5) they are not indented.

% test.tex
\DocumentMetadata{lang=en-GB,tagging=on}
\documentclass{article}
\begin{document}
abc
\end{document}

$ latexmk -lualatex test.tex

$ show-pdf-tags --xml --xmp test.pdf | grep -A5 '<XMP>'
 <XMP>

<?xpacket begin="" id="W5M0MpCehiHzreSzNTczkc9d"?>
<x:xmpmeta xmlns:x="adobe:ns:meta/">
 <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
  <rdf:Description rdf:about=""

$ show-pdf-tags --version
show-pdf-tags version: 1.5