v0.13.7-pl.1

Bug fix — keep cursor + tooltip on top after redraws

drawChart removes the per-redraw elements (axes, curve, ticks, labels) and appends fresh ones at the end of the SVG's children list. The cursor and tooltip groups are persistent across redraws, so on every redraw after the first (resize, font load, …) they ended up at the start of the children list and were painted over by the freshly-drawn curve — making the tooltip's numbers unreadable wherever the curve passed through.

Fix

• Expose group on CursorElements.
• Re-append both the cursor and tooltip groups after every drawChart so they always sit at the end of the children list. SVG paints in document order — later elements appear on top.