allow users to manually check their games validity

[climu]

As discussed in #348 it could be helpful for our members to be able to check their sgf by them self. We just need to create a public view like those without the save and delete buttons:

https://github.com/climu/openstudyroom/blob/e00b57456ad9b8389a039f5ca07ab7768e2ee2f0/league/views.py#L840-L841