add pythonBoolean syntax

syntax/python.vim

   syn keyword pythonPreCondit   as
   syn match   pythonFunction    "[a-zA-Z_][a-zA-Z0-9_]*" display contained
 else
-  syn keyword pythonStatement   as nonlocal False None True
+  syn keyword pythonStatement   as nonlocal
+  syn keyword pythonBoolean     True False None
   syn match   pythonFunction    "\%([^[:cntrl:][:space:][:punct:][:digit:]]\|_\)\%([^[:cntrl:][:punct:][:space:]]\|_\)*" display contained
 endif
 
   HiLink pythonHexError         Error
   HiLink pythonBinError         Error
 
+  HiLink pythonBoolean          Boolean
+
   HiLink pythonBuiltinObj       Structure
   HiLink pythonBuiltinFunc      Function