htmlpageheader - bolding unicode

[MoVoDesign]

Prerequisites

• I have searched for similar issues in both open and closed tickets and cannot find a duplicate.
• The issue still exists against the latest master branch of yii2-mpdf.
• This is not an usage question. I confirm having gone through and read the documentation.
• This is not a general programming / coding question. (Those should be directed to the webtips Q & A forum).
• I have attempted to find the simplest possible steps to reproduce the issue.
• I have included a failing test as a pull request (Optional).

Steps to reproduce the issue

1. render a ('mode' => Pdf::MODE_UTF8) pdf with content:

    <htmlpageheader name="otherpages">
    <b>a 記試</b> / <i>b 記試</i> / <span style="font-weight: bold">c 記試</span>
    </htmlpageheader>

Expected behavior and actual behavior

When I follow those steps, I see the Chinese characters above with normal font weight: a 記試

I was expecting bold font-weight: a 記試

Please note
Bold Chinese fonts work in other parts of the pdf generated

Environment

OSX 12.6 / PHP 8.0.23

yiisoft/yii2                          2.0.46
kartik-v/yii2-mpdf             dev-master 6a6506e

Browsers

• Google Chrome
• Mozilla Firefox
• Internet Explorer
• Safari

Operating System

• Windows
• Mac OS X
• Linux (CentOS)
• Mobile

Libraries

• jQuery version: 2.1.4
• yii2-mpdf version: dev-master 6a6506e

Isolating the problem

• This bug happens on the demos page
• The bug happens consistently across all tested browsers
• This bug happens when using yii2-mpdf without other plugins (no other PDF plugins)