Use `yamlfix` for autoformatting yaml files

[approxit]

As we use black for code auto-formatting, only python files are covered. Other files like yaml are not auto-formatted hence each IDE formats a few bits differently, making unnecessary noise. To mitigate that, let's use something like https://github.com/lyz-code/yamlfix to have auto-formatting in yaml files too.

[approxit]

Unfortunately, yamlfix is not handling comments formatting well.