feat(logger): support pretty JSON output

[joshamaju]

Summary

• add optional numeric or string indentation to JsonFormatter
• preserve compact JSON output by default
• add formatter coverage, a runnable example, documentation, and a patch changeset

Validation

• pnpm test
• pnpm run typecheck
• pnpm run typecheck:examples
• pnpm run build
• pnpm run example:pretty-json

[changeset-bot]

🦋 Changeset detected

Latest commit: 82303ac

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@jamx/logger	Patch

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