adding proton 6.3 + fixing the config

[myyc]

Hi, this fixes two issues:

• it adds proton 6.3 support (trivial)
• the config file isn't always read. i implemented a solution to make sure that protonenv always tries to read it from config.json. it's not the best solution ever but it's the best i could come up with without refactoring.
  thanks for making this, by the way