Add dll path for windows in launch config json

[antontsvil]

Changes:

For easier setup in Windows environments, include an env variable for PATH rather than LD_LIBRARY_PATH which seems to be specific to Linux.

Legal Stuff:

By submitting this pull request, I confirm that...

• My changes may be used in a future commercial release of Rogue Legacy
• I will be credited in a CONTRIBUTORS file and the "GitHub Friends"
  section of the credits for all of said releases, but will NOT be compensated
  for these changes unless there is a prior written agreement

[flibitijibibo]

I don't recall the syntax but I think we can do both by adding an OS check - I'd have to look it up. Still, definitely okay with merging this if we can get both Linux and Windows build environments working at the same time.

[antontsvil]

ooh an OS check would be ideal. This line could also just as easily be added to the README until then.

Is the os check thing something you can do in launch json? I'm more familiar with intellij

[flibitijibibo]

According to SO it appears to just be "windows": and "linux": blocks:

https://stackoverflow.com/questions/54982502/how-to-target-platforms-with-launch-json

[antontsvil]

Easy enough - made the change and seems to work just fine! Have yet to double check it still works in linux though

[flibitijibibo]

lgtm - congratulations on being the first successful RL1 PR!