Create an email reporter

[tarkatronic]

🚀 Feature Request

Is your feature request related to a problem? Please describe.

I want more avenues for reporting out the vulnerabilities that we're gathering!

Describe the solution you'd like

Following on #5, we should be able to report out to emails, same way as we are currently to Slack. This would mean:

• Overall summary email -- Go to infosec team maybe?
• Team summary email -- Go to each team individually
  • This could also contain a breakdown per repo
• Unconfigured/unknown repo email -- Probably also go to infosec team

Describe alternatives you've considered

A thing does exist for this already. GitHub will send out a weekly Dependabot email. But I don't think that works well for this case. For that, you have to be "watching" the repositories, which requires all users to take (potentially many) actions. That email is also limited to only Dependabot, and we want to support more sources.