Feature: Drag'n'Drop emoji from iOS keyboard

## Description

A cool feature of the iOS keyboard is the ability to insert emoji using drag and drop

https://github.com/user-attachments/assets/f8d5df91-c45d-4be5-85bf-571239c6871f

Most editors recognize this action as inserting a file, but native inputs handle it as inserting text.

Lexical doesn't respond to the drop emoji

https://github.com/user-attachments/assets/6c109075-a173-4ee6-bca1-a67e72d557c6

## Impact

This is probably not a common use case for inserting emoji, but it would be convenient for iOS users if it were supported

Start by reproducing the iOS keyboard emoji drag-and-drop action in Lexical and compare it with a native input, using the attached examples as the expected behavior. Trace the editor's drop handling to identify why the emoji is ignored; done means the dropped emoji is inserted as text without regressing other drop behavior.

Written by the indexing model from the issue text.