Mark everything outside active as inert (and aria-hidden) so assistive
tech and the keyboard cannot reach the background while an overlay is open.
Walks up the ancestor chain from active to the body, marking each
element's other children. Returns a disposer that restores the prior state.
Mark everything outside
activeasinert(andaria-hidden) so assistive tech and the keyboard cannot reach the background while an overlay is open. Walks up the ancestor chain fromactiveto the body, marking each element's other children. Returns a disposer that restores the prior state.