chore: add test id for drawer header back arrow button

Author: wklos-iohk

src/design-system/side-drawer/side-drawer-content-header.component.tsx

@@ -31,7 +31,10 @@ export const Header = ({
     >
       {onBackClick !== undefined && (
         <Flex w="$40">
-          <NavigationButtons.Back onClick={onBackClick} />
+          <NavigationButtons.Back
+            onClick={onBackClick}
+            data-testid="drawer-header-back-button"
+          />
         </Flex>
       )}
       <Flex justifyContent="center" w="$fill">