feat: add boolean-to-string entrypoint with custom toString method

[tijnjh]

Boolean#toString() returns 'true' | 'false' instead of string

[Copilot]

Pull request overview

This PR introduces a new boolean-to-string entrypoint that narrows Boolean#toString() to the literal string output ("true" / "false"), and wires it into the package’s public entrypoints (including recommended) via the export map.

Changes:

• Add src/entrypoints/boolean-to-string.d.ts to narrow Boolean#toString() to `${boolean}`.
• Include the new entrypoint in src/entrypoints/recommended.d.ts.
• Export ./boolean-to-string from package.json so consumers can import it directly.

Reviewed changes

Copilot reviewed 1 out of 3 changed files in this pull request and generated no comments.

File	Description
src/entrypoints/recommended.d.ts	Includes the new boolean-to-string entrypoint in the recommended bundle.
src/entrypoints/boolean-to-string.d.ts	Adds a global Boolean interface augmentation narrowing toString() to `"true"
package.json	Adds a new ./boolean-to-string export pointing to the built artifacts in dist/.

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