Create CODEOWNER file for python.props file (#6725)

* Create CODEOWNER

* nit; renaming to CODEOWNERS

More info [here](https://github.blog/2017-07-06-introducing-code-owners/)

Author: vrdmr

CODEOWNERS

@@ -0,0 +1,10 @@
+# See https://help.github.com/articles/about-codeowners/
+# for more info about CODEOWNERS file
+#
+# It uses the same pattern rule for gitignore file
+# https://git-scm.com/docs/gitignore#_pattern_format
+#
+
+
+# Adding codeowner for Python specific files such that GitHub automatically adds python folks as a reviewer.
+build/python.props @vrdmr @Hazhzeng