Function parse_pnpm_catalog_data 

pub fn parse_pnpm_catalog_data(source: &str) -> PnpmCatalogData

Parse the catalog sections of a pnpm-workspace.yaml file.

Returns an empty PnpmCatalogData when the file has no catalog data, when the YAML is malformed, or when the catalog sections are present but empty. All non-catalog top-level keys (packages, catalog, catalogs, etc.) are ignored.