Add Drag Event in Context.

For people to be able to implement their own scripts to import drag drop files.

"Code" example:

if bpy.context.window_manager.drags:

for filepath in bpy.context.window_manager.drags:
      bpy.ops.import_scene.fbx(filepath = filepath)
      bpy.ops.import_scene.obj(filepath = filepath)
      bpy.ops.import_scene.gltf(filepath = filepath)
      # import images, other