Document new configuration option (#9526)

The configuration option was added in getsentry/sentry-javascript#11153.

Co-authored-by: vivianyentran <[email protected]>

Author: soerface

docs/platforms/javascript/common/user-feedback/configuration/index.mdx

@@ -63,6 +63,7 @@ Most text that you see in the default Feedback widget can be customized.
 | `messageLabel`       | `Description`                          | The label for the feedback description input field.                |
 | `messagePlaceholder` | `What's the bug? What did you expect?` | The placeholder for the feedback description input field.          |
 | `successMessageText` | `Thank you for your report!`           | The message to be displayed after a succesful feedback submission. |
+| `isRequiredText`     | `(required)`                           | The text displayed next to a required field.       |
 
 Example of customization: