Adjust event position based on timeZone prop

[jackstenglein]

Fixes #276.

The event positioning will now be adjusted based on the timeZone prop, as they were in version 2.7.x. I've also updated the default event editor so that it accounts for the timeZone prop. Users of a custom editor will have to handle that on their own side still.

The changes to App.tsx are for ease of testing and can be reverted when you feel this is ready to merge.

[aldabil21]

Hi @jackstenglein
I've finally checked this out
LGTM 🚀
I've found 2 issues to close this

1. The default selectedDate, we need to get it out of the Object.assign and explicitly set it with getTimeZonedDate. example selectedDate: getTimeZonedDate(selectedDate || new Date(), props.timeZone)
2. The start time of the Cell will cause issue when dropping event into a Cell, we need to revertTimeZonedDate in useCellAttributes hook, just like to did with the Editor submit function.

If you want to test above issue, steps:

1. Choose any other timezone than your local zone.
2. Create an event in 1am cell, its good 👍🏽
3. Drag & drop it to 2am, the event will increase/decrease the hour differences

Let me know if you can patch these changes

Edit: I've let myself do that, cheers