New egg: libyaml

Hi,

I'd like to add a new egg `libyaml` to online packages,
the release-info URI is:
- https://codeberg.org/rikuri/libyaml.ss/releases/download/latest/libyaml.ss.release-info

The egg is to parse yaml.
About the existing egg `yaml`,
there are issues about distinguish list, mapping, NULL, etc.
So I specifically defined the yaml object in scheme:
- https://codeberg.org/rikuri/libyaml.ss/src/branch/main/docs/usage.md#yaml-and-scheme

and libyaml is based on it.

Best, Luli