libxml2-utils not listed as debian documentation requirement

[gilbertbw]

When building the documentation, just for embedded use

export KERL_BUILD_DOCS=yes
export KERL_INSTALL_HTMLDOCS=no
export KERL_INSTALL_MANPAGES=no

I noticed the following error in the output

DOCUMENTATION INFORMATION (See: /home/gilbert/.asdf/plugins/erlang/kerl-home/builds/asdf_25.3.2/otp_build_25.3.2.log)
 * documentation  :
 *                  xmllint is missing.
 *                  Using fakefop to generate placeholder PDF files.

I see that xmllint is provided by the libxml2-utils package. This is listed here https://github.com/asdf-vm/asdf-erlang/blob/6744df773596ec681792ca112ff0c495af63de75/README.md?plain=1#L75-L76

But not in any of the sections above. I think it should be against building the documentation?

n.b. I don't seem to be having any issue using the embedded documentation after building, so I guess it's only required for the HTML help?