Dark mode in Bootstrap 5.3

Bootstrap 5.3 introduced support for dark mode. This note describes how to use it in a Vite project.

Install Bootstrap 5.3 and Popper.js:

$ pnpm add bootstrap@5.3.0-alpha1 @popperjs/core

Set data-bs-theme="dark" on the <html> element:
```
<html data-bs-theme="dark">
```