feat(legend): allow legend text to be copyable (#877)

fixes #710

Author: rshen91

src/components/legend/_legend_item.scss

@@ -5,7 +5,6 @@ $legendItemVerticalPadding: $echLegendRowGap / 2;
   display: flex;
   flex-wrap: nowrap;
   justify-content: space-between;
-  user-select: none;
   align-items: center;
   width: 100%;