add proposal of CancellationError, https://github.com/microsoft/vscode/issues/93686

src/vs/workbench/api/common/extHost.api.impl.ts

@@ -1212,6 +1212,9 @@ export function createApiFactoryAndRegisterActors(accessor: ServicesAccessor): I
 			ViewColumn: extHostTypes.ViewColumn,
 			WorkspaceEdit: extHostTypes.WorkspaceEdit,
 			// proposed api types
+			get CancellationError() {
+				return errors.CancellationError;
+			},
 			get RemoteAuthorityResolverError() {
 				// checkProposedApiEnabled(extension);
 				return extHostTypes.RemoteAuthorityResolverError;