fix: unable to evaluate instanceof AjaxError

Author: voliva

src/internal/ajax/errors.ts

@@ -37,7 +37,7 @@ export interface AjaxError extends Error {
   response: any;
 }
 
-export interface AjaxErrorCtor {
+export interface AjaxErrorCtor extends Function {
   /**
    * Internal use only. Do not manually create instances of this type.
    * @internal
@@ -77,7 +77,7 @@ export const AjaxError: AjaxErrorCtor = createErrorClass(
 
 export interface AjaxTimeoutError extends AjaxError {}
 
-export interface AjaxTimeoutErrorCtor {
+export interface AjaxTimeoutErrorCtor extends Function {
   /**
    * Internal use only. Do not manually create instances of this type.
    * @internal