mmultiscripts spacing between children is too narrow

Issue Summary

mmultiscripts children should have more spacing between them than what MathJax currently does (although I can't recall the proper values).

MathJax 4 output:

Firefox's native output:

Firefox's output is not necessarily the expected one, but there should at least some spacing between the children.

OS: Windows 11
Browser: Mozilla Firefox 153.0

Steps to Reproduce:

Use the code to render:

<math xmlns="http://www.w3.org/1998/Math/MathML">
    <mmultiscripts>
        <mi>A</mi>
        <mn>1</mn>
        <mn>2</mn>
        <mn>3</mn>
        <mn>4</mn>
        <mprescripts/>
        <mn>7</mn>
        <mn>300</mn>
        <mn>3</mn>
        <mn>700</mn>
    </mmultiscripts>
</math>

Technical details:

• MathJax Version: 4
• OS: Windows 11
• Browser: Mozilla Firefox 153.0

I am using the default MathJax configuration and loading MathJax via

<script src="https://cdn.jsdelivr.net/npm/mathjax@4/tex-mml-chtml.js" defer></script>

Start by running the provided MathML reproduction with the default MathJax 4 configuration and compare its mmultiscripts spacing with Firefox's output. Trace the mmultiscripts rendering path and determine the intended spacing values; the issue is done when the children have appropriate visible separation without regressing the supplied example.