add Croissant data description

croissant.json

@@ -0,0 +1,33 @@
+{
+  "@context": "https://mlcommons.org/croissant/1.0/context.json",
+  "@type": "Dataset",
+  "name": "ssl4eo_eu_forest",
+  "description": "Multi-temporal forest segmentation dataset with GeoTIFF stacks and masks.",
+  "data": {
+    "@type": "FileSet",
+    "fileStructure": {
+      "@type": "ParquetFile",
+      "url": "index.parquet",
+      "fields": [
+        {
+          "name": "sample_id",
+          "type": "string",
+          "description": "Unique identifier for each sample."
+        },
+        {
+          "name": "image_paths",
+          "type": "array",
+          "items": {
+            "type": "string"
+          },
+          "description": "List of paths to multi-temporal GeoTIFF images."
+        },
+        {
+          "name": "mask_path",
+          "type": "string",
+          "description": "Path to the segmentation mask."
+        }
+      ]
+    }
+  }
+}