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

kf_config.json

@@ -1,15 +1,19 @@
 {
   "library_name": "kerasformers",
-  "kerasformers_version": "1.1.3",
+  "kerasformers_version": "1.2.1",
   "model_module": "kerasformers.models.efficientnet_lite",
   "model_class": "EfficientNetLiteImageClassify",
   "variant": "tf_efficientnet_lite1_in1k",
   "weights": "model.weights.h5",
+  "schema_version": 2,
+  "weight_dtype": "float32",
   "model_type": "efficientnet_lite",
-  "width_coefficient": 1.0,
-  "depth_coefficient": 1.1,
-  "dropout_rate": 0.2,
-  "default_size": 240,
-  "image_size": 240,
-  "num_classes": 1000
+  "vision_config": {
+    "width_coefficient": 1.0,
+    "depth_coefficient": 1.1,
+    "dropout_rate": 0.2,
+    "default_size": 240,
+    "image_size": 240,
+    "num_classes": 1000
+  }
 }