As taken from the checker after uploading the master .zip
Upload successful with errors
"Ghostium - 2.3.2" uploaded successfully but some errors were detected. You are still able to use and activate the theme. Here's your report...
Errors
(Very recommended to fix, functionality could be restricted)
The usage of {{meta_description}} in HTML head is no longer required
package.json property "name" must be lowercase
The property "name" in your package.json file must be lowercase.
Good examples are: "my-theme" or "theme" rather than "My Theme" or "Theme".
Check the package.json documentation for further information.
As taken from the checker after uploading the master .zip