chore: add sample for rejecting drag start outside chartArea

[kurkle]

closes #611

[github-actions[bot]]

Size Change: +4 B (+0.02%)

Total Size: 20.5 kB

Filename	Size	Change
dist/chartjs-plugin-zoom.esm.js	7.44 kB	-1 B (-0.01%)
dist/chartjs-plugin-zoom.js	7.58 kB	-2 B (-0.03%)
dist/chartjs-plugin-zoom.min.js	5.51 kB	+7 B (+0.13%)

_{compressed-size-action}