Add model index metadata for TTS inference

.model-index/metadata.json

@@ -0,0 +1,15 @@
+{
+  "task_categories": [
+    {
+      "name": "audio",
+      "subtasks": [
+        {
+          "name": "text-to-speech"
+        }
+      ]
+    }
+  ],
+  "language": "bn",
+  "library_name": "transformers",
+  "pipeline_tag": "text-to-speech"
+}