test: extend test coverage and update configuration

[halvaradop]

Description

This pull request expands the test coverage within the project, particularly for the merge function, verifySelectorTheme, and removeEmptyProperties utilities. It introduces new and basic tests to ensure the accuracy and robustness of these functions. Additionally, it refines the test coverage report by updating the exclude patterns. Key changes:

• Exclude tsup.config.base.ts and all *.test files from coverage reports
• Add conditional to merge function
• Add new tests for merge function
• Increase coverage for verifySelectorTheme utility function
• Add test for removeEmptyProperties utility function

Checklist

• Added documentation.
• The changes do not generate any warnings.
• I have performed a self-review of my own code
• All tests have been added and pass successfully

Notes

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Thank you, @halvaradop, for your contribution to halvaradop/tailwindcss-utilities.

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