Add external resource to the View Transitions API

[umaar]

Description

Adds a link to a community resource on view transitions.

Motivation

❓ Why are you making these changes and how do they help readers?

• It gives readers an alternative perspective on view transitions, e.g. some demos, videos, code examples.
• This change is being made on behalf of my employer, in an effort to share what we believe is a useful resource.