Active state should be passed by prop instead of guessed by the component

[gfellerph]

Context

Components like the <post-tabpanel> or the <post-mainnavigation> can contain items with an active state that's based on the currently active URL.

Decision

What is the change that we're proposing and/or doing?

Consequences

What becomes easier or more difficult to do because of this change?

Example (optional)

If applicable, show a code example to support the decision.