added dataset_dict.json for one-liner load_dataset()

dataset_dict.json

@@ -0,0 +1,16 @@
+{
+  "splits": {
+    "train": {
+      "name": "train",
+      "num_examples": 19783
+    },
+    "validation": {
+      "name": "validation",
+      "num_examples": 1795
+    },
+    "test": {
+      "name": "test",
+      "num_examples": 1844
+    }
+  }
+}