[runes] (fix) Add missing constants file

robots-at-runes/research/constants.py

+from pathlib import Path
+
+from research_common.constants import DSET_DIR
+
+RUNES_DATASET_DIR: Path = DSET_DIR / "runes"
+
+
+RUNES_DATASET_DIR.mkdir(exist_ok=True, parents=True)