Give saveAsExcel its own config options (#20647)

Co-authored-by: Ben Russell <russellben@microsoft.com>

src/sql/platform/query/common/query.ts

@@ -12,6 +12,9 @@ export interface IQueryEditorConfiguration {
 			readonly textIdentifier: string,
 			readonly encoding: string
 		},
+		readonly saveAsExcel: {
+			readonly includeHeaders: boolean,
+		},
 		readonly saveAsXml: {
 			readonly formatted: boolean,
 			readonly encoding: string