fix: add experimental feature note to TTFD docs (#8955)

Co-authored-by: vivianyentran <20403606+vivianyentran@users.noreply.github.com>

Author: armcknight

src/platforms/apple/common/performance/instrumentation/automatic-instrumentation.mdx

@@ -339,6 +339,12 @@ The span finishes after the view appeared on the screen.
 
 ## Time to Full Display
 
+<Note>
+
+This feature is experimental and may have bugs.
+
+</Note>
+
 _(New in version 8.4.0)_
 
 Time to full display provides insight into how long it takes your view controller to launch and load all of its content, by adding a span for each launch of a view controller. The SDK sets the span operation to `ui.load.full-display` and the span description to the view controllers' name followed by `full display`, for example, `MainActivity full display`.