This script adds the missing auto-dark mode to the new theme feature of Bootstrap 5.3.
It switches the Bootstrap theme automatically between light and dark mode, depending on the system settings, if you set the data-bs-theme attribute of your <html> to auto.
Use it by just including bootstrap-auto-dark-mode.js in your header and setting data-bs-theme to auto.
<html lang="en" data-bs-theme="auto">
<head>
<!-- your code -->
<script src="./src/bootstrap-auto-dark-mode.js"></script>
</head>
<!-- your code -->
<!-- […] -->