Add .clang-format

[StellaSmith]

I have format-on-save enabled on my editor, and since this project's code style differs from my default I had to disable in this project.

[xissburg]

This would be nice to have, but I am lazy and it will take a while to get the configuration right. I'll give it a shot.

[xissburg]

I have tried setting up a .clang-format in this project but was unable to find a satisfying configuration. It can be difficult because there are places where I want a certain aesthetic but the exact same formatting is enforced on every file. E.g. there are specific parts where I want the assignments to be aligned. I am not sure if that can be achieved.

[killerdevildog]

PR #143