feat: add marketplace callout component

[lancesnider]

1. This PR creates a reusable snippet for linking to marketplace demos.
2. Add analytics tracking to marketplace links from this component and demo cards.

Example

Here's the new snippet in action: https://rive-editor-examples.mintlify.app/editor/animate-mode/animating-draw-order

Usage

1. Publish the demo to the Marketplace using the support at Rive user account (credentials in 1password).
2. Import the component and define the href value.

import { Marketplace } from '/snippets/marketplace.mdx'

<Marketplace
  href="https://rive.app/community/files/26116-48795-animating-draw-order"
/>

[lancesnider]

Unrelated to this PR, but this isn't actually used.

[lancesnider]

Unrelated to this PR, but I added docs for how to use the other common snippets as well.