Add a clang-format format file

[theoparis]

I was looking to make a improved version of #50, which I needed to have implemented along with the knob widget change for a mini DAW implementation. I was also considering making a SDL3 GPU api PR in the future if no one else does it. However, I noticed that there is no .clang-format file and I am assuming the defaults for clang-format would mess up any PR that it is applied to.

This would probably introduce some formatting changes, but it would make it easier to contribute if formatting on saving is enabled (a feature in most IDEs). This also means there would be a standard for styling code, instead of just saying it has to be "consistent".

[RobLoach]

Feel free to submit a .clang-format that makes closely to what's currently there.