3 - Add DNS Monitor source and implementations

[aloftus23]

fixes #196
fixes #285

🗣 Description

Added DNSMonitor to the pe-source module --> collects domain permutations and domain alerts from the DNSMonitor API.

Updated the pe-reports mudule to pull in DNSMonitor data and display findings in the P&E report.

💭 Motivation and context

Allows P&E to collect data from DNSMonitor and display findings.

🧪 Testing

Passes pytests and pre-commit checks.

✅ Pre-approval checklist

• This PR has an informative and human-readable title.
• Changes are limited to a single goal - eschew scope creep!
• All future TODOs are captured in issues, which are referenced
  in code comments.
• All relevant type-of-change labels have been added.
• I have read the CONTRIBUTING document.
• These code changes follow cisagov code standards.
• All relevant repo and/or project documentation has been updated
  to reflect the changes in this PR.
• Tests have been added and/or modified to cover the changes in this PR.
• All new and existing tests pass.

[lgtm-com]

This pull request introduces 1 alert when merging b0862a8 into 78ccbfd - view on LGTM.com

new alerts:

• 1 for Variable defined multiple times

[coveralls]

Coverage decreased (-0.08%) to 24.403% when pulling 1c87c7d on AL-dnsmonitor into dd5a870 on develop.