message: Align message context menu to right
  This changes the message context menu to align the right edge of the menu with
  the right edge of the button that opens it, which should keep all menu options
  inside the viewport, even if they are very wide.
  Part of
diff: @@ -71,7 +71,7 @@ export default class MessageActionBar extends React.PureComponent {
  // The window X and Y offsets are to adjust position when zoomed in to page
  const x = buttonRect.right + window.pageXOffset;
  - const y = (buttonRect.top + (buttonRect.height / 2) + window.pageYOffset) - 19;
  + const y = buttonRect.bottom + window.pageYOffset;
  const { getTile, getReplyThread } = this.props;
  const tile = getTile && getTile();
  @@ -83,9 +83,10 @@ export default class MessageActionBar extends React.PureComponent {
  }
  createMenu(MessageContextMenu, {
  - chevronOffset: 10,
  mxEvent: this.props.mxEvent,
  - left: x,
  + chevronFace: "none",
  + // Align the right edge of the menu to the right edge of the button
  + right: window.innerWidth - x,
  top: y,
  permalinkCreator: this.props.permalinkCreator,
  eventTileOps: tile && tile.getEventTileOps ? tile.getEventTileOps() : undefined,
  