An additional route for a for adding a attachment to a task.

This is hopefully a smaller request than implementing all items that can appear in the ➕ menu, assuming s (added with Shift + Enter) are like attachments too.

This also builds off my request for editing a task body. I would be able to edit this directly by replacing it. https://www.taskade.com/feedback/public-api/p/update-taskcontent-route

I would also want to be able to . For reading a .