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

kf_config.json

@@ -1,23 +1,29 @@
 {
   "library_name": "kerasformers",
-  "kerasformers_version": "1.1.3",
+  "kerasformers_version": "1.2.1",
   "model_module": "kerasformers.models.owlvit",
   "model_class": "OwlViTDetect",
   "variant": "owlvit-base-patch32",
   "weights": "model.weights.h5",
+  "schema_version": 2,
+  "dtype": "float32",
   "model_type": "owlvit",
-  "vision_image_size": 768,
-  "vision_patch_size": 32,
-  "vision_hidden_dim": 768,
-  "vision_intermediate_size": 3072,
-  "vision_num_layers": 12,
-  "vision_num_heads": 12,
-  "text_hidden_dim": 512,
-  "text_intermediate_size": 2048,
-  "text_num_heads": 8,
+  "text_config": {
+    "hidden_dim": 512,
+    "intermediate_size": 2048,
+    "num_heads": 8,
+    "num_layers": 12,
+    "max_position_embeddings": 16,
+    "vocab_size": 49408
+  },
+  "vision_config": {
+    "image_size": 768,
+    "patch_size": 32,
+    "hidden_dim": 768,
+    "intermediate_size": 3072,
+    "num_layers": 12,
+    "num_heads": 12
+  },
   "projection_dim": 512,
-  "text_num_layers": 12,
-  "text_max_position_embeddings": 16,
-  "text_vocab_size": 49408,
   "image_size": null
 }