Resolve Lint Issues Related to Whitespace/Prettier and Secrets

[Matthew-Grayson]

🗣 Description

Exclude test snapshots from trailing-whitespace
Exclude dev.env.example from detect-private-key
Apply fixes from end-of-file-fixer, prettier, and trailing-whitespace

💭 Motivation and context

Closes issue #91

🧪 Testing

I recommend reviewing these changes in unified view (vs split view).

All tests pass.
Pre-commit checks pass.

✅ 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.

✅ Pre-merge checklist

• Revert dependencies to default branches.
• Finalize version.

✅ Post-merge checklist

• Create a release.

[schmelz21]

approved. prettier linter passing.

[nickviola]

LGTM. Prettier does pass now when pulling down and running locally.