How to append a newline after every match using xmlint --xpath

Question

I have the following HTML code:

1</script>
<ins class="adsbygoogle"
     style="display:block"
     data-ad-client="ca-pub-5408099190056760"
     data-ad-slot="7305827575"
     data-ad-format="auto"
     data-full-width-responsive="true"></ins>
<script>
     (adsbygoogle = window.adsbygoogle || []).push({});
</script>        </div>
      </div>
      
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                <span>2021-01-02 01:57</span>
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<p>Try this patch, which provides 2 options:</p>

<ul>
<li><p><code>--xpath</code>: same as old <code>--xpath</code>, with nodes separated by <code>\n</code>.</p></li>
<li><p><code>--xpath0</code>: same as old <code>--xpath</code>, with nodes separated by <code>\0</code>.</p></li>
</ul>

<p>Test input (<code>a.html</code>):</p>

<pre><code><textarea name="command" class="setting-input   fixed-width" rows="9">12

Test command 1:

# xmllint --xpath '//textarea[@name="command"]/text()' --html a.html

Test output 1:

 1
 2

Test command 2:

# xmllint --xpath0 '//textarea[@name="command"]/text()' --html a.html | xargs -0 -n1

Test output 2:

 1
 2