a quick fix for mathjax

[boomzero]

What does this PR aim to accomplish?:

This pull request includes a small change to the XMOJ.user.js file. The change ensures that MathJax is rendered on the problem page.

How does this PR accomplish the above?:

• XMOJ.user.js: Added a call to RenderMathJax() in the async function main() to render MathJax when the pathname is /problem.php.

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[github-actions]

Qodana for JS

1 new problem were found

Inspection name	Severity	Problems
Missing await for an async function call	◽️ Notice	1

💡 Qodana analysis was run in the pull request mode: only the changed files were checked
☁️ View the detailed Qodana report

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