Support for component animations

[mcoker]

trafficstars

Placeholder for the core work in https://github.com/patternfly/patternfly/issues/4979

If the animations can be handled all in CSS, there may be no react work needed, but we may need to introduce things like event handlers to watch, for example, transitionend before removing an element from the DOM or adding/removing a class.

[stale[bot]]

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