Upgrade kf_config.json to v2 (nested config + weight_dtype)

kf_config.json

@@ -1,19 +1,23 @@
 {
   "library_name": "kerasformers",
-  "kerasformers_version": "1.1.3",
+  "kerasformers_version": "1.2.1",
   "model_module": "kerasformers.models.res2net",
   "model_class": "Res2NetImageClassify",
   "variant": "res2net50_26w_8s_in1k",
   "weights": "model.weights.h5",
+  "schema_version": 2,
+  "weight_dtype": "float32",
   "model_type": "res2net",
-  "depth": [
-    3,
-    4,
-    6,
-    3
-  ],
-  "base_width": 26,
-  "scale": 8,
-  "cardinality": 1,
-  "num_classes": 1000
+  "vision_config": {
+    "depth": [
+      3,
+      4,
+      6,
+      3
+    ],
+    "base_width": 26,
+    "scale": 8,
+    "cardinality": 1,
+    "num_classes": 1000
+  }
 }