Dropping text file onto the textview should open it or insert its contents not its filename

### What Happened?

Dropping files from a filemanager (for example) onto the Code text view inserts the filename into the target document. Other Text editors (Gnome Text Editor, AbiWord) either opens the file as a document or insert the contents into the existing document.

### Steps to Reproduce

1. Drop a text file onto a Code document
2. The filename is inserted

### Expected Behavior

The contents of the file should be inserted, either into a new document or into the target document at the drop point (not sure which).

### OS Version

8.x (Circe)

### Session Type

Classic Session (X11, This is the default)

### Software Version

Latest release (I have run all updates)

### Log Output

```shell

```

### Hardware Info

_No response_