Weird wrapping in the header for some generic classes

[Hixie]

e.g.
https://master-api.flutter.dev/flutter/rendering/ContainerRenderObjectMixin-mixin.html
...looks like this:

[srawlins]

Oof, I almost fell out of my seat looking at that. Good find.

Some preliminary notes:

• This flex layout, mixed with horizontal list items and white-space: nowrap is a little weird... probably deserves a refactoring into something... simpler?
• adding flex: 1 to the ol.breadcrumbs improves the UI.
• adding white-space: normal to .signature also helps.
• dropping white-space: nowrap from span.type-parameter I think also helps.
• I think we're managing too much of the layout with white-space:. That's an uphill battle.

[jcollins-g]

Yikes. I think in general having type information in the breadcrumbs is going to lead to trouble, particularly if the information is repeated in the header right below it. Maybe we can "fix" this by removing type parameters from breadcrumbs and linkifying the header. A further refinement might be to separate out the type parameters from the header somehow so that the header doesn't have similar readability problems.