[docs] Textfield floating label limitation

mui#16847 (comment)

docs/src/pages/components/text-fields/text-fields.md

@@ -94,6 +94,8 @@ other styles to meet the specification.
 
 ## Limitations
 
+### Shrink
+
 The input label "shrink" state isn't always correct.
 The input label is supposed to shrink as soon as the input is displaying something.
 In some circumstances, we can't determine the "shrink" state (number input, datetime input, Stripe input). You might notice an overlap.
@@ -109,6 +111,11 @@ or
 <InputLabel shrink>Count</InputLabel>
 ```
 
+### Floating label
+
+The floating label is absolutely positioned, it won't impact the layout of the page.
+You need to make sure that the input is larger than the label to display correctly.
+
 ## Integration with 3rd party input libraries
 
 You can use third-party libraries to format an input.