[Idea] Upload improvement

[mdziczkowski]

Please add following elements:

1. button to start upload, in case the upload doesn't start automatically for any reasons

2. possibility to also upload files from locations that aren't GitHub (people usually don't store schematics there, but they do on other locations).

Above will improve much how the site works

[theacodes]

I'm totally open to this, I just don't have time to work on it at the moment. If someone wants to send a PR, I'd be happy to review.