Parse PyPI classifiers

Parsing the PyPI classifiers is sometimes needed to determine the license.

Example (fastapi):
```json5
{
    "info": {
        // ...
        "classifiers": [
            // ...
            "License :: OSI Approved :: MIT License",
            "Operating System :: OS Independent",
            "Typing :: Typed"
            // ...
        ],
        // ...
    },
    // ...
}
```