Add a few links

src/source/online.rst

 Online Resources
 ================
 
-TODO a list of MNT Reform related websites and communities.
+You can follow the status of the MNMT project from the following links:
+
+- `The official MNT website <https://mntre.com>`_
+- `Follow MNT on the Fediverse <https://mastodon.social/@mntmn>`_
+- `View the MNT Git repository <https://source.mntmn.com/MNT>`_
+- `The MNT CrowdSupply page <https://www.crowdsupply.com/mnt>`_