Feature Proposal: Animate expanding/collapsing of rows

[chapati23]

Right now, rows are expanded/collapsed by toggling display: none via javascript. the display-property can't be animated unfortunately.

a quick win would be to apply css-classes expanded & collapsed instead of setting it via javascript. this way users could add animations themselves by simply overwriting the display: none css with an animation of their choice (e.g. animating the height from 0 to 100% or using some sort of transform)

[afc163]

PR welcomes if you need animation badly.