feat: add scope flag

[ramcguire]

The repeatable scope flag only includes and validates variables on an allowlist/opt-in basis.

[codecov-commenter]

⚠️ Please install the to ensure uploads and comments are reliably processed by Codecov.

Codecov Report

❌ Patch coverage is 92.80000% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 93.64%. Comparing base (13e6e82) to head (5206ad4).

Files with missing lines	Patch %	Lines
src/main.rs	90.10%	9 Missing ⚠️
❗ Your organization needs to install the Codecov GitHub app to enable full functionality.

Additional details and impacted files

@@             Coverage Diff             @@
##             main       #5       +/-   ##
===========================================
+ Coverage   80.00%   93.64%   +13.64%     
===========================================
  Files           2        2               
  Lines         520      614       +94     
===========================================
+ Hits          416      575      +159     
+ Misses        104       39       -65     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.