`config` crate relies on an unmaintained crate

[devkelley]

The config crate relies on an unmaintained crate (yaml-rust). This crate either needs to be updated or replaced to eliminate the security alert that it generates.

This was originally detected in #89, where the warning was ignored in .github/workflows/security_audit.yaml.

References:

rust-cli/config-rs#473
https://rustsec.org/advisories/RUSTSEC-2024-0320
Tasks:

• config crate is updated or replaced and the yaml-rust crate is no longer part of the dependency tree
• security_audit.yaml is updated to remove the ignored advisory