Add a checkbox for empty file option to web interface

[VisLab]

Could a checkbox be added to add the option to ignore issue 99 which is the empty raw file ignore. This would allow users to try validating the examples using the web-interface.

[sappelhoff]

I think it would be more sustainable to add a second "upload" button, where users can upload a bids-validator-config.json file.

If you want to ignore issue 99, you would then format that file as such:

{
	"ignore": [99]
}

EDIT: However, users can also just add a .bids-validator-config.json to their dataset before upload, and that will be used :thinking: so perhaps some documentation about that will be enough.