New Component: aside for examples

[alexandrascript]

⚠️ This is for feature requests with the https://developer.chrome.com site, not Chromium itself. If you want to file a bug with Chromium (the open-source project behind Google Chrome and other browsers), please use https://crbug.com.

Is your feature request related to a problem? Please describe.

I often share examples in documentation which would be best served as an aside. Codelabs have one already, and I think we could benefit from a "Story" or "In Example" aside.

Describe the solution you'd like

New {% Aside %} component. I propose the Timeline or Book svg.

Describe alternatives you've considered

I've been using the regular Aside, but that is easily lost or skipped.

Additional context Add any other context or screenshots about the feature request here.

[rachelandrew]

I think this looks useful, in the spirit of normalizing the two sites if we add it here we should also add it to web.dev.