In the Graphic Styles panel, Shift-click and Cmd/Ctrl-click both added
or removed the one style clicked. Shift-click now adds to the selection
every style from the last one clicked without Shift through the
clicked one, in the order the panel lists them, and Cmd/Ctrl-click
still adds or removes one. A plain click applies the style and selects
it alone, Alt-click still adds it on top, and the Control bar's Style
picker still applies on every click.
The panel uses swatches::click_selection, as the Swatches panel and
the library panel do.
Docs: docs/target-app-parity.md.