[3P Views Template - Cards]

We've updated the **Cards** dev doc as a sample template that is easier to scan and read. The current page has endless vertical scroll and appears overloaded with information.

We have made the following changes to the doc:

* Added a TOC that automatically displays sections up to H3 on the right side of the page.
* Revised the content flow to make it more logical.
* Structured the content into collapsible sections to make the doc easily scannable and readable.
* Reduced size of the images to minimize vertical scroll.

PiperOrigin-RevId: 740618817

Author: Material Design Team