Add support for a bootstrap theme

[jonasstrehle]

⭐ Suggestion

UIX should provide a bootstrap.ts theme under src/themes that comes with the bootstrap styles and JS functionality.
To allow for dark/light mode switches the data-bs-theme attribute as seen in this example should be connected to the UIX.Theme.mode

• Integrate support for a custom theme called bootstrap
• Allow for dark/light mode toggle
• Allow for JS functionality as provided by Bootstrap (such as Toasts, Dropdowns, etc.)
• Create a UIX template project under unyt-org/uix-template-bootstrap
• Add information to Styles and Themes section of the developer documentation

Additional resources:

• Docs for bootstrap can be found here
• Themes in uix/src/themes/
• Theme manager in uix/base/theme-manager.ts

📃 Motivating Example

see #52