Create Addon should warn about not initialised git submodule`s

[Lypsolon]

Is there an existing issue for this?

• I have searched the existing issues.

Please describe the feature you have in mind and explain what the current shortcomings are?

You can build the Addon and upload it to the server even if some submodules haven't been initialised.
This causes uploading a broken add-on and getting this info on the server to be too late.

How would you imagine the implementation of the feature?

Add a subprocess.run into the create a package file that runs ´git submodule update --init --recursive` for you to ensure all the submodules are initialised.

• Check if this creates problems when you check out a branch or a different commit than the one set in the .gitmodules file.

Are there any labels you wish to add?

• I have added the relevant labels to the enhancement request.

Describe alternatives you've considered:

No response

Additional context:

No response