versatile-data-kit: Include DL join link

After this change, members of the VMware organization
can join the DL by clicking on the link provided in the
contact section. Unfortunately, we couldn't find a trivial
way to automate the join process for non-members, so a new
group was established which external users can email to
request to join. This can probably be automated through
some script (see the python-dev DL for inspiration),
but this is not a priority as we don't expect there to
be an overwhelming surge of users looking to join our
mailing list.

Signed-off-by: gageorgiev <[email protected]>

README.md

@@ -49,8 +49,9 @@ Official documentation for Versatile Data Kit can be found [here](https://github
 If you are interested in contributing as a developer, visit [CONTRIBUTING.md](CONTRIBUTING.md).
 
 # Contacts
-You can reach out to us through mail, or join our public Slack workspace using the following [invite link](https://join.slack.com/t/versatiledata-rgg2437/shared_invite/zt-tvnl62c3-qP0EUYJZJxb6Ws_eQWyDtQ).
-
+You can join our public Slack workspace by clicking [here](https://join.slack.com/t/versatiledata-rgg2437/shared_invite/zt-tvnl62c3-qP0EUYJZJxb6Ws_eQWyDtQ).
+Members of the VMware organization can join our mailing list by clicking [here](https://outlook.office365.com/owa/[email protected]/groupsubscription.ashx?action=join&source=Exchange&guid=7fa73da4-dc79-4579-b0a1-6c96e6143e8f).
+External users can request to join the mailing list by emailing [here](mailto:[email protected]?subject=Invite%20me%20to%20the%20VDK%20mailing%20list).
 
 # Code of Conduct
 Everyone interacting in the project's source code, issue trackers, slack channels, and mailing lists is expected to follow the [Code of Conduct](CODE-OF-CONDUCT.md).