Added Cache Control Headers (CRASM-667)

[hawkishpolicy]

• Added Cache-Control header with a timeout of 60 minutes in an effort to prevent Users from needing to 'hard reset' their browser after updates to Production.

🗣 Description

• Amended app.ts, docs.js, and api.js with custom middleware.
• Cache-Control headers are set to 'private, must-revalidate, max-age=3600

💭 Motivation and context

• Closes CRASM-667

🧪 Testing

• Tested locally.
• Chrome appears to be calling for new resources once max-age is hit.
• Will know if this fixes the hard reset problem once the it is merged and a new PR follows it.

✅ 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 new and existing tests pass.

✅ Pre-merge checklist

• Revert dependencies to default branches.
• Finalize version.

✅ Post-merge checklist

• Create a release.