Update the output file name with more descriptive qualities

[ameliav]

🗣 Description

This PR resolves issue #28 and adds a more descriptive pdf file name for the generated report.

💭 Motivation and context

To make the pdf file name unique to the assessment and date of generation.

🧪 Testing

Run the script as usage suggests and verify output references are replaced.

✅ Pre-approval checklist

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

✅ Pre-merge checklist

• [x] Revert dependencies to default branches.
• [x] Finalize version.

✅ Post-merge checklist

• [ ] Create a release.

[coveralls]

Pull Request Test Coverage Report for Build 6187518960

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 0.0%

---

Totals
Change from base Build 6176502958:	0.0%
Covered Lines:	0
Relevant Lines:	0

---

💛 - Coveralls