Update current.cursor references to current[cursorStateField]?

[milesingrams]

Not sure if this was intended, but since the cursorStateField is customizable I figured the references to current.cursor should be changed to current[cursorStateField]. I may not understand the code fully though so apologies if this is there for a reason.

https://github.com/yjs/y-prosemirror/blob/984175f7fd7960b1478f10370829659f001ccd3b/src/plugins/cursor-plugin.js#L127-L132

[DAlperin]

This is fixed by https://github.com/yjs/y-prosemirror/pull/88