Add the BF16 delta data types in constants.py

Author: Srihari-mcw

gguf-py/gguf/constants.py

@@ -1166,6 +1166,8 @@ class GGMLQuantizationType(IntEnum):
     Q4_0_4_4 = 31
     Q4_0_4_8 = 32
     Q4_0_8_8 = 33
+    Q4_0_B16 = 34
+    Q8_0_B16 = 35
 
 
 # TODO: add GGMLFileType from ggml_ftype in ggml.h