aiocsv: add build-aiocsv.yml for riscv64 wheels

[luhenry]

• Package: aiocsv
• Version: 1.4.1
• Source: https://github.com/MKuranowski/aiocsv
• Docs: https://github.com/MKuranowski/aiocsv

Compiles the aiocsv._parser CPython extension (a hand-written C module bundled in the sdist, no Cython step needed). Upstream publishes no riscv64 wheel.

Mirrors upstream's deploy.yml, built from the checkout the same way, and wires in the test suite from upstream's separate test.yml since deploy.yml itself doesn't test wheels.

Differs from upstream

• Builds musllinux_riscv64 alongside manylinux - only runtime/test dep is typing_extensions/aiofiles/pytest, all pure-Python, no numpy-shaped blocker (gotcha 221).

Testing

• Runs upstream's pytest suite (aiofiles, pytest, pytest-asyncio) against the built wheel.

License: OK

Built on cp312; 61 passed, 0 skipped.