Ask to reload external changes

[Cammin]

Currently, if an actively open LDtk project has its file externally changed from source control or another program, then it requires closing LDtk and relaunching it to reload the changes.

I think a nice option for the app would be to prompt the user if they would like to reload any external changes, with a disclaimer that any current unsaved work would be lost.

Something like a prompt like this: