message: matrix dropdown collapse/expand icon css
  ref surveyjs/survey-creator#2317
diff: @@ -244,9 +244,13 @@ export var defaultV2Css = {
  cell: "sd-table__cell",
  headerCell: "sd-table__cell sd-table__cell--header",
  rowTextCell: "sd-table__cell sd-table__cell--row-text",
  + detailButton: "sd-table__cell--detail-button",
  + detailButtonExpanded: "sd-table__cell--detail-button--expanded",
  + detailIcon: "sd-detail-panel__icon",
  + detailIconExpanded: "sd-detail-panel__icon--expanded",
  detailIconId: "icon-expanddetail",
  detailIconExpandedId: "icon-collapsedetail",
  -
  + actionsCell: "sd-table__cell sd-table__cell--actions"
  },
  matrixdynamic: {
  mainRoot: "sd-element sd-question sd-row__question sd-question--complex sd-question--table",
  