docs(react-native): Add attachAllThreads option (#17266)

## DESCRIBE YOUR PR

Documents the new `attachAllThreads` option for React Native on iOS,
which attaches full stack traces for all threads to captured events.
Added in the Hybrid SDK Options section alongside the existing
`attachThreads` (Android) option.

Ref: getsentry/sentry-react-native#5959
SDK PR: getsentry/sentry-react-native#5960

## IS YOUR CHANGE URGENT?

- [ ] Urgent deadline (GA date, etc.):
- [ ] Other deadline:
- [x] None: Not urgent, can wait up to 1 week+

⚠️ Should be merged after
getsentry/sentry-react-native#5960 is released

## PRE-MERGE CHECKLIST

- [ ] Checked Vercel preview for correctness, including links
- [ ] PR was reviewed and approved by any necessary SMEs (subject matter
experts)
- [ ] PR was reviewed and approved by a member of the [Sentry docs
team](https://github.com/orgs/getsentry/teams/docs)

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: antonis

docs/platforms/react-native/configuration/options.mdx

@@ -377,6 +377,12 @@ Set this boolean to `true` to automatically attach all threads to all logged eve
 
 </SdkOption>
 
+<SdkOption name="attachAllThreads" type="boolean" defaultValue="false">
+
+Set this boolean to `true` to attach full stack traces for all threads to all captured events on iOS. Requires `attachStacktrace` to be enabled (default: `true`).
+
+</SdkOption>
+
 <SdkOption name="enableAnrFingerprinting" type="boolean" defaultValue="true">
 
 When enabled, ANR events whose stacktraces contain only system frames (for example, `java.lang` or `android.os`) are assigned a static fingerprint and grouped into a single issue, rather than creating many separate issues. Set this to `false` to restore per-stacktrace ANR grouping.