Adding a type guard for AxiosError (#2949)

Co-authored-by: Jason Kwok <JasonHK@users.noreply.github.com>

index.d.ts

@@ -153,6 +153,7 @@ export interface AxiosStatic extends AxiosInstance {
   isCancel(value: any): boolean;
   all<T>(values: (T | Promise<T>)[]): Promise<T[]>;
   spread<T, R>(callback: (...args: T[]) => R): (array: T[]) => R;
+  isAxiosError(payload: any): payload is AxiosError;
 }
 
 declare const axios: AxiosStatic;