feat!: add special CSV deck field, comment support and skip fields by mapping to the empty string

BREAKING CHANGE: deck in CSV is now not a field but a special value for the per-note deck pattern. Additionally, lines starting with hash in CSV are now ignored for better Anki compatibility.

export_apkgs/__init__.py

+from .config import load_apkg_spec
+from .exporter import ApkgExporter
+from pathlib import Path
+from tempfile import TemporaryDirectory
+import argparse
+
+def export_package_from_spec(spec_path: Path, args: argparse.Namespace) -> Path:
+    with TemporaryDirectory() as intermediate_dir:
+        package_directory = spec_path.parent
+        spec = load_apkg_spec(spec_path)
+        exporter = ApkgExporter(
+            spec=spec,
+            content_dir=package_directory,
+            intermediate_dir=Path(intermediate_dir),
+            args=args
+        )
+        return exporter.export()