fix(core): Mark package as side-effect free

[devclaimjuimperai]

📢 Type of change

• Bugfix
• New feature
• Enhancement
• Refactoring

📜 Description

Adds "sideEffects": false to @sentry/react-native's package.json, same as @sentry/core, @sentry/react and @sentry/browser already have.

I grepped src/js for anything that runs at import time. The only top-level calls are in src/js/tools/ (metro config, babel transformer, collect-modules script), and those get loaded by Node directly, never bundled into the app. Nothing else patches globals on import.

💡 Motivation and Context

Fixes getsentry/sentry#126410. Without the flag, importing even just SDK_VERSION drags most of the SDK into the bundle with esbuild/Rollup/webpack (and Expo's tree shaking).

💚 How did you test it?

Ran the repro from the issue against the published 8.29.0, with and without the flag patched into its package.json (I also had to mark promise/* as external):

	input files	output bytes
before	121	87303
after	3	972

📝 Checklist

• I added tests to verify changes.
• No new PII added or SDK only sends newly added PII if sendDefaultPII is enabled.
• I updated the docs if needed.
• I updated the wizard if needed.
• All tests passing.
• Public API changes reviewed by another Mobile SDK team member or implemented according to the develop docs spec.
• No breaking changes.

🔮 Next steps