feat: Add synced crosshairs

[DaveSkender]

Fixes #141
Try again with new v2.0, may need to fork and update AbelHeinsbroek/chartjs-plugin-crosshair.

To do:

• get sync groups working, so it spans across charts (see workaround)
• refactor all typings stuff, it's a mess
• legend params for placeholders not filled
• add settings option to turn off (off by default)

this may require a Fork n' Fix of the plugin

• internalize fixed variant of this plugin

[cloudflare-pages]

Deploying stock-charts with    Cloudflare Pages

Latest commit:	54eb904
Status:	✅  Deploy successful!
Preview URL:	https://edf87f60.stock-charts.pages.dev
Branch Preview URL:	https://crosshairs.stock-charts.pages.dev

View logs

[DaveSkender]

Current situation is that the crosshairs work; however, they're no longer syncing across charts like they used to (before we had to remove with charts.js v4 incompatible upgrades).

[DaveSkender]

Had to take the code in and modify it to get it to work with newer chart.js versions and to sync; but it works. The sync across charts is a bit flakey if you move too fast. It also oddly doesn't reach the last bar.

• consider removing entirely or replacing with a better custom option