Add Session Replay docs to .NET MAUI page

[sentry-junior]

Session Replay is supported for .NET MAUI but is not documented on the MAUI SDK page, leaving customers unaware the feature is available.

• Add a Session Replay section to the MAUI docs page covering setup, configuration, and any platform-specific caveats
• Verify parity with Session Replay docs on other mobile SDK pages (e.g. iOS, Android)

Action taken on behalf of U0A81HHRKHU.

[linear-code]

DOCS-2895