Fix type error for consumers on @types/react v19 (#409)

React.ReactText was removed from @types/react v19. It was an alias for
string | number, so substitute the underlying types directly so the
SubMenuProps.title declaration keeps compiling against both v18 and v19.

Author: fatadel

src/index.d.ts

@@ -48,7 +48,7 @@ declare module "@firefox-devtools/react-contextmenu" {
     }
 
     export interface SubMenuProps {
-        title: React.ReactElement<any> | React.ReactText,
+        title: React.ReactElement<any> | string | number,
         attributes?: React.HTMLAttributes<HTMLDivElement>,
         className?: string,
         disabled?: boolean,