Note marker feature

[forsbergplustwo]

It would be great to support a Note marker style feature, where you can add notes to graphs on certain dates. For example, you may want to add a note marker on the date that you made a pricing change or update your Shopify App Store listing.

• Add a note marker resource (date, note text, optional association to to specific app_title). index, new, create, update, destroy.
• User option to include note markers on main graph
• Update main chart to show the note markers as vertical line marker, with hover showing text