Issue #3261163 by bnjmnm, Spokje, longwave, nod_: Update to PostCSS 8

core/misc/dialog/off-canvas/css/base.css

core/misc/dialog/off-canvas/css/button.css

core/misc/dialog/off-canvas/css/details.css

core/misc/dialog/off-canvas/css/dropbutton.css

core/misc/dialog/off-canvas/css/form.css

core/misc/dialog/off-canvas/css/messages.css

core/misc/dialog/off-canvas/css/reset.css

core/misc/dialog/off-canvas/css/table.css

core/misc/dialog/off-canvas/css/tabledrag.css

core/misc/dialog/off-canvas/css/throbber.css

core/misc/dialog/off-canvas/css/titlebar.css

core/misc/dialog/off-canvas/css/utility.css

core/misc/dialog/off-canvas/css/wrapper.css

core/modules/layout_builder/css/layout-builder.css

core/modules/layout_builder/css/off-canvas.css

core/modules/workspaces/css/workspaces.off-canvas.css

core/modules/workspaces/css/workspaces.toolbar.css

core/package.json

core/themes/claro/css/base/print.css

core/themes/claro/css/components/accordion.css