2D: Mention custom points in migration guide


QtCharts to Graphs2D migration guide did not mention Graphs2D's flexible
point customization possibilities. This patch mentions
XYSeries::pointDelegate in the migration guide.

Pick-to: 6.12 6.8
Fixes: QTBUG-147168
Change-Id: I3a731619d7c8a8607ed203b59025762f1c773b7f
Reviewed-by: Tomi Korpipaa <tomi.korpipaa@qt.io>
commitf9b45803bebafce2c9acd2ba8db118a08878729a
parent35689240d8087ded7a286fdd3ad93a31b7aceba8
authorSami Varanka <sami.varanka@qt.io>
committerSami Varanka <sami.varanka@qt.io>
commit timeFri, 2 Oct 2026 05:25:21 +0000