Add .kicad_pcb to upload

[Libermentix]

Problem

Many users love that they can use us as a storage backup. So far, when using the legacy upload (using .kicad_pcb), we store the original file. When users use the KiCad Push they however upload all files in an export format. Hence in case of a data loss they would not be able to recover their files

Solution

Upload the .kicad_pcb together with all required files, allowing customers to download that data later.