Add sample rate configuration

[buenaflor]

📜 Description

💡 Motivation and Context

Closes: #141

💚 How did you test it?

📝 Checklist

You have to check all boxes before merging:

• I reviewed the submitted code.
• I added tests to verify the changes.
• No new PII added or SDK only sends newly added PII if sendDefaultPII is enabled.
• I updated the docs if needed.
• Review from the native team if needed.
• No breaking change or entry added to the changelog.

🔮 Next steps

[github-actions]

	Fails
🚫	Please consider adding a changelog entry for the next release.

	Messages
📖	Do not forget to update Sentry-docs with your feature once the pull request gets approved.

Instructions and example for changelog

Please add an entry to CHANGELOG.md to the "Unreleased" section. Make sure the entry includes this PR's number.

Example:

## Unreleased

- Add sample rate configuration ([#144](https://github.com/getsentry/sentry-kotlin-multiplatform/pull/144))

If none of the above apply, you can opt out of this check by adding #skip-changelog to the PR description.

Generated by 🚫 dangerJS against 9e3bae0

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Files	Coverage Δ
...platform/extensions/SentryOptionsExtensions.jvm.kt	66.66% <100.00%> (+2.15%)	⬆️
...in/io/sentry/kotlin/multiplatform/SentryOptions.kt	100.00% <100.00%> (ø)

📢 Thoughts on this report? Let us know!