Add Hugging Face config for download tracking

HF download tracking requires a file named "config.json". Since the snapshot_download() function we use downloads the whole repo, this placeholder is sufficient. Only tracked the first time it is downloaded on a machine.

config.json

@@ -0,0 +1,4 @@
+{
+  "model_type": "parcae-countdown",
+  "version": "v1"
+}