Encoding ISO-8859-1 is not supported

[alexismanuel]

Problem Statement
xq fails to parse XML files that use ISO-8859-1 encoding when piping content through the command line using cat. The tool lacks support for non-UTF-8 character encodings, specifically throwing an error when encountering ISO-8859-1 encoded XML files.

Steps to Reproduce

1. Create a test XML file (test.xml) with the following content:

<?xml version="1.0" encoding="ISO-8859-1"?>
<a>toto</a>

Run the command:

cat test.xml | xq -x /a

Actual Result
The command fails with the following error:

Error: xml: encoding "ISO-8859-1" declared but Decoder.CharsetReader is nil

Expected Result
The command should successfully parse the XML file and output:
toto

The error suggests that the XML decoder lacks the necessary character set reader implementation to handle ISO-8859-1 encoding. This should either be supported directly or the tool should provide clear documentation about supported encodings and potential workarounds for users dealing with non-UTF-8 encoded XML files.