Come with a pattern for os-specific versions

[AMDmi3]

Some project use different versioning schemes depending on OS, for instance https://repology.org/project/zotero/information. Need to split these, probably the same way as we split unrelated projects. Need some back end support, including adding platform/os field, filling it from parsers and/or repository configs, and checking it in the ruleset. Also, would be nice to come with a more consistent naming scheme, such as name@suffix, after ensuring that @ never happens in actual names.