Feature/clang format

[isdampe]

This PR adds support for running clang-format across the code base to enforce the coding conventions developed earlier by @lachfoy.

Because clang-format will need to be manually installed on user systems, running the code formatter isn't required - it's just a way of tidying up code as developers deem necessary. Hopefully this is the best of both worlds - not introducing friction in environment setup for future new developers - but also giving a handy tool for anyone who wants to use it.

An entry in the Makefile has been added for running the formatter across the whole project - make format. Be warned - it will re-write files - so ensure you've committed or backed up files if you want to revert the styling.

And for proof of concept, I've run make format on the main branch. It does tidy the code base up nicely...

[lachfoy]

Which version of clang-format are you using? I've run into errors trying to run the format target:

The formatting that has been applied looks great, though!

[isdampe]

Hey @lachfoy - I'm using clang-format version 14.0.6. Could you list the invalid argument errors here? We might get away with just removing them from the file.