• feat #2671 subgrid now propagate events to topmost grid. Use el.gridstackNode.grid to know which (sub) grid.
• fix #3028 updateOptions() no longer modifies passed in struct. only field we check are being handled too.
• fix #3029 resizeToContent() fix for nested grid with content above
• fix #3030 resizeToContentCheck() wasn't blocking _ignoreLayoutsNodeChange at end of the loop
• rem #3022 removed ES5 support (IE doesn't support CSS vars needed now)
• rem #3027 remove legacy code support for disableOneColumnMode, oneColumnSize, oneColumnModeDomSort