Add Session Replay docs for Kotlin Multiplatform

[lindsayrpiper]

The Kotlin Multiplatform SDK (sentry-kotlin-multiplatform) includes SentryReplayOptions but docs/platforms/kotlin/ has no session-replay section.

• All other mobile SDKs with replay support have dedicated docs (Android, Apple, Flutter, React Native)
• Related: Add Session Replay docs to .NET MAUI page #18254 tracks the same gap for .NET MAUI

[linear-code]

DOCS-2902

[sfanahata]

@lindsaypiper I'll need more information about this request. Our Kotlin SDK actually just points to using Either Java or Android SDKs, and Android is the one with replay of all of them. I'm not sure why they're calling out that Multiplatform has a replay option. It doesn't seem to exist.

So for them, they'll need to use Android, which is well documented with that feature.

[lindsayrpiper]

@sfanahata seems like this might now be duplicated in getsentry/sentry-kotlin-multiplatform#562