Enforce formatting

[myurkin]

We have description of the code style - https://github.com/adda-team/adda/wiki/CodeStyleGuide. But it is neither comprehensive (covers all cases) nor enforced. It would be great to implement testing for the style in Github Actions - probably some existing standard can be adopted for that. And, naturally, it should be as much close to the existing de-facto style as possible.

The first step is to study existing standards for C code, and whether they are readily available in IDEs and automatic tools.

[myurkin]

/cc @palatni