Update request-signatures.md

added the content for prefill draw widget.

Author: pravinOpenSign

docs/docs/help/New-Document/request-signatures.md

@@ -119,7 +119,7 @@ The **Prefill Widgets** feature lets document creators prefill specific fields b
 - **Radio Button** – Prefill with a selected choice  
 - **Checkbox** – Prefill as checked or unchecked  
 - **Image** – Insert a default image (e.g., logo or stamp) 
-
+- **Draw** – Allows the user to draw directly in this widget; use it when a prefill drawing is required.
 ---
 
 ### Add Widgets for Signers