erp5: add typing egg

https://pypi.org/project/typing/ a backport of python > 3.5 typing
module

With this module, we can already write type annotations in python 2 (
https://mypy.readthedocs.io/en/latest/cheat_sheet.html ) and give hints
to jedi.

stack/erp5/buildout.cfg

@@ -519,6 +519,7 @@ eggs = ${neoppod:eggs}
   pylint
   jedi
   yapf
+  typing
   pytracemalloc
   xlrd
 
@@ -835,3 +836,5 @@ jedi = 0.15.1
 parso = 0.5.1
 
 yapf = 0.28.0
+
+typing = 3.7.4.1