feat: --modules option.

[knightedcodemonkey]

• Puts transforms of module globals behind the --modules option.
• Adds test for npm monorepo (workspaces).
• Updates the docs.
• Closes #46

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 98.30%. Comparing base (4815dc1) to head (4d9f9c0).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #47 +/- ## ========================================== + Coverage 98.18% 98.30% +0.12% ========================================== Files 3 3 Lines 385 413 +28 ========================================== + Hits 378 406 +28 Misses 7 7 ```

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