ZDoom runner patch

Hi, im new here but the Lutris project is great. I noticed that in zdoom runner (zdoom.py) is a litle bug that prevents freedoom from working. In get_executable() should be join($runner_dir,“zdoom/zdoom”) instead of join($runner_dir, ‘zdoom’), i hope it helps.

I noticed that just after the release of Lutris 0.3.8 which results in a broken zdoom runner until 0.4.0 is released :confused: