Add CHD Support

[Ronald-Diemicke]

So - I'm in a similar boat to #3 - I've backed up my discs to CHD... and this just puts an extra step in where I need to convert to ISO... Would be nice if the launcher just allowed for CHDs too!

[xTVaser]

This would have to happen in the main repo, not the launcher, and it's come up before. #465

This is unlikely to happen as it's another dependency we have to add to the project, and our first step of working with the ISO is to fully extract it (so the space saving benefits of CHD are irrelevant). The one thing that will be added to the launcher eventually is to ability to work with files/folders directly instead of an ISO file (the issue you are referencing).