Add the highlight of Python arrow '->'

It adds the highlight of the arrow from the type hint system.

after/syntax/python.vim

@@ -11,6 +11,7 @@ syntax keyword pythonOdysseyBoolean  True False
 syntax keyword pythonOdysseyBuiltin  int float bool str bytes
 syntax keyword pythonOdysseySelf     self
 syntax keyword pythonOdysseyPrint    print
+syntax match   pythonOdysseyArrow    '->'
 syntax match   pythonOdysseyFunction '\<\l\w*\>('me=e-1
 syntax match   pythonOdysseyType     '\<\u\w*\>'
 syntax keyword pythonStatement       class nextgroup=pythonOdysseyClass skipwhite