Feature: Industry directory text filter (#10518)

src/widgets/industry_widget.h

@@ -37,6 +37,7 @@ enum IndustryDirectoryWidgets {
 	WID_ID_DROPDOWN_CRITERIA,    ///< Dropdown for the criteria of the sort.
 	WID_ID_FILTER_BY_ACC_CARGO,  ///< Accepted cargo filter dropdown list.
 	WID_ID_FILTER_BY_PROD_CARGO, ///< Produced cargo filter dropdown list.
+	WID_ID_FILTER,               ///< Textbox to filter industry name.
 	WID_ID_INDUSTRY_LIST,        ///< Industry list.
 	WID_ID_SCROLLBAR,            ///< Scrollbar of the list.
 };