[libxml2] xmllint: Document --quiet option

[Nick Wellnhofer <nwellnhof src gnome org>]

commit fec85df14d22d8047e40221f8d56e22549cba8e6
Author: Nick Wellnhofer <wellnhofer aevum de>
Date:   Tue Sep 6 18:50:23 2022 +0200

    xmllint: Document --quiet option

 doc/xmllint.xml | 8 ++++++++
 1 file changed, 8 insertions(+)
---
diff --git a/doc/xmllint.xml b/doc/xmllint.xml
index 73b325a9..2f5fe8ba 100644
--- a/doc/xmllint.xml
+++ b/doc/xmllint.xml
@@ -66,6 +66,7 @@
                <group choice="opt">
                        <arg choice="plain"><option>--version</option></arg>
                        <arg choice="plain"><option>--debug</option></arg>
+                       <arg choice="plain"><option>--quiet</option></arg>
                        <arg choice="plain"><option>--shell</option></arg>
                        <arg choice="plain"><option>--xpath "<replaceable 
class="option">XPath_expression</replaceable>"</option></arg>
                        <arg choice="plain"><option>--debugent</option></arg>
@@ -482,6 +483,13 @@
        </listitem>
                </varlistentry>
 
+               <varlistentry>
+       <term><option>--quiet</option></term>
+       <listitem>
+               <para>Don't print informational messages to stderr.</para>
+       </listitem>
+               </varlistentry>
+
                <varlistentry>
        <term><option>--recover</option></term>
        <listitem>