Git/Github is free. What you need to do is clone the Pak128.Britain-Ex repository (search for instructions on how to do this) to your own repository on Github, and add your modified files to your cloned repository. You then push your changes (the addition of your files and changes to any existing files - if you are adding new vehicles rather than just adding liveries, do not forget to add translation texts for each new vehicle to en.tab also) to your repository on Github. I can then merge your changes into my branch on Github so that these are automatically compiled.
While you do not need to provide compiled versions, you do need to compile them yourself to test that they work, as you need to be the person testing/debugging your new additions.