feat(apple): Add docs for beforeCaptureScreenshot (#10152)

Adds docs for the beforeCaptureScreenshot callback for the Cocoa SDK.

Author: philipphofmann

platform-includes/enriching-events/attach-screenshots/apple.mdx

@@ -13,3 +13,38 @@ SentrySDK.start { options in
   options.attachScreenshot = YES;
 }];
 ```
+
+### Customize Screenshot Capturing
+
+<Note>
+
+Requires Cocoa SDK version `8.27.0` or higher.
+
+</Note>
+
+
+The `beforeCaptureScreenshot` also allows you to customize the behavior based on event data, so you can decide when to capture a screenshot and when not to. The callback doesn't work for crash events.
+
+```swift {tabTitle:Swift}
+import Sentry
+
+SentrySDK.start { options in
+    options.dsn = "___PUBLIC_DSN___"
+    options.beforeCaptureScreenshot = { event in
+        // Return false to not capture a screenshot for the event.
+        return false
+    }
+}
+```
+
+```objc {tabTitle:Objective-C}
+@import Sentry;
+
+[SentrySDK startWithConfigureOptions:^(SentryOptions *options) {
+    options.dsn = @"___PUBLIC_DSN___";
+    options.beforeCaptureScreenshot = ^BOOL(SentryEvent * _Nonnull event) {
+        // Return NO to not capture a screenshot for the event.
+        return NO;
+    };
+}];
+```