fix: enabling pan after chart initialization

[kurkle]

fix #834

Also change some lint rules so optional chaining can be used.

[github-actions]

Size Change: +366 B (+1.69%)

Total Size: 22 kB

Filename	Size	Change
dist/chartjs-plugin-zoom.esm.js	8.41 kB	+150 B (+1.82%)
dist/chartjs-plugin-zoom.js	8.56 kB	+151 B (+1.79%)
dist/chartjs-plugin-zoom.min.js	5.01 kB	+65 B (+1.31%)

_{compressed-size-action}