add auto_map for custom config class

config.json

@@ -76,5 +76,8 @@
     "rms_norm_eps": 1e-05,
     "spatial_merge_size": 2
   },
-  "vocab_size": 120818
+  "vocab_size": 120818,
+  "auto_map": {
+    "AutoConfig": "configuration_brain_ocr.BrainOCRConfig"
+  }
 }