Add an Animated Sidebar component

[beetlejusse]

The library currently provides a single Sidebar component. I would like to propose
an additional Sidebar variant to give users an alternative design to choose from.
The proposed component is fully prop-driven and animated, built with motion and
Tailwind CSS (compatible with both v3 and v4), and follows the library's existing
single-file, copy-paste convention.

Motivation

Offering more than one Sidebar design would broaden the range of navigation layouts
available to users. The proposed variant differs from the existing implementation in
the following respects:

• Nav items can be organized into expandable/collapsible groups with a staggered
  reveal animation.
• A shared-layout active indicator transitions smoothly between items.
• A desktop rail-collapse mode is supported, with icon tooltips when collapsed.
• A mobile slide-in drawer with a backdrop is included.

[DavidHDev]

I'll see what i can do! :)

[beetlejusse]

Awesome! If you're okay with it, I'd be happy to implement it and submit a PR.

[DavidHDev]

For the moment new components aren't being accepted from the outside, but I'll work on something and add it!

[beetlejusse]

Totally understand! If you'd be open to making an exception, I'd be happy to add the demo here first. Either way, I'll completely respect your decision.