Add spec-compliant config.json files

xnnpack/config.json

@@ -0,0 +1,18 @@
+{
+  "$schema": "https://huggingface.co/software-mansion/react-native-executorch-spec/resolve/main/config.schema.json",
+  "model": "whisper_base",
+  "family": "whisper",
+  "capabilities": [
+    "speech-to-text"
+  ],
+  "backend": "xnnpack",
+  "license": "apache-2.0",
+  "variants": [
+    {
+      "file": "whisper_base_xnnpack_fp32.pte",
+      "precision": "fp32",
+      "quantized": false,
+      "default": true
+    }
+  ]
+}