message: add getModifiers input helper
diff: @@ -10,7 +10,7 @@ import { Vec2 } from '../../mol-math/linear-algebra';
  import { BitFlags, noop } from '../../mol-util';
  -function getButtons(event: MouseEvent | Touch) {
  +export function getButtons(event: MouseEvent | Touch) {
  if (typeof event === 'object') {
  if ('buttons' in event) {
  return event.buttons
  @@ -37,6 +37,15 @@ function getButtons(event: MouseEvent | Touch) {
  return 0
  }
  +export function getModifiers(event: MouseEvent | Touch) {
  + return {
  + alt: 'altKey' in event ? event.altKey : false,
  + shift: 'shiftKey' in event ? event.shiftKey : false,
  + control: 'ctrlKey' in event ? event.ctrlKey : false,
  + meta: 'metaKey' in event ? event.metaKey : false
  + }
  +}
  +
  export const DefaultInputObserverProps = {
  noScroll: true,
  noContextMenu: true,
  