Improve styling of the example/s graphics API callout

[doup]

Examples

• Use callout component to style the web graphics API warning.

Example

• Use callout component to style the web graphics API warning.
• Add callout--plain modifier that hides the callout top border.
• Change link to it goes directly to the example and not the listing.

[mockersf]

if you're touching this callout, something that I would like is a way to switch between webgl2/webgpu on the same example without going through the index page

[doup]

Makes sense, I've updated the example page link.