DS3: Update the setup docs to be more up to date

[Moonlington]

What is this fixing or adding?

There's a discrepancy between the instructions on the archipelago site and the instructions that are mostly given in the discord community. The current main way to downpatch the game is to only copy over the downpatched DarkSoulsIII.exe instead. I have changed the docs to reflect that.

I have also adjusted the formatting of the docs to be a bit nicer to look at. If there's any more proposed changes let me know.