Add Google's timeline to the README around the targetSdkVersion enforcement

[fabiendem]

Summary

Clarify the calendar around the requirements for the Android targetSdkVersion bump. Google now always follows the same cadence for the requirements around the targetSdkVersion bump on the Google Play Store: the next version is required on August 31st, the year after the SDK update's release, if you want to ship a new app, or if you want to keep shipping updates for an existing app.

See https://support.google.com/googleplay/android-developer/answer/11926878?sjid=11853000253346477363-EU#zippy=%2Care-there-any-exceptions-for-existing-apps-targeting-api-or-below

So we can expect the targetSdkVersion: 35 to be enforced on August 31st 2025.

I also rephrased

Currently, the latest version of React Native targets SDK 34, so this isn't an issue yet, but it will be in a future release.

to

Currently, the latest version of React Native targets the Android SDK 34.

The original sentence suggests that if React Native targets the SDK 35, your app must target the SDK 35 no matter what. But even if React Native targets the SDK 35, you can always force your app to keep targeting the SDK 34 until August 31st 2025. Ultimately, you maintain control of this parameter until the deadline.
This is different than the minSdkVersion.

Test Plan

This is a README change. It renders as expected and has no typos.

What's required for testing (prerequisites)?

• Proofread
• Understand Google's calendar

What are the steps to test it (after prerequisites)?

N/A

Compatibility

N/A

OS	Implemented
iOS	✅
Android	✅

Checklist

• [] I have tested this on a device and a simulator - N/A
• [x] I added the documentation in README.md
• [] I added a sample use of the API in the example project (example/src/App.tsx) - N/A

[zoontek]

@fabiendem Thanks for this, you are right about apps targetting SDK 34. I commited a few changes, WDYT?