Alternative for rules YAML format

[banditopazzo]

serde-yaml has been archived, so we have to replace it.

There are 2 options:

• replace it with something like yaml-rust2 keeping yaml syntax
• completely change the format to another format (for example TOML, etc.)

Honestly I am in favor of the second option, and in particular to TOML, because it's well supported.

[vadorovsky]

Yes, +1 for TOML from me.