add vulnerability alerts

[philschatz]

Currently only Admins can see the vulnerability alerts for a repo. This changes it so that everyone is aware of them.

By letting everyone see them, the thinking is that they will be fixed sooner.

TODO

• Update those settings for all the repos.
  • Maybe this could be done using a script. See https://github.com/openstax/napkin-notes/tree/master/phil/tools or the staxly's settings plugin