Updating typings

The first argument in `axios.interceptors.response.use` is optional, in the case that you just want to intercept an error.

Ex:

```ts
axios.interceptors.response.use(undefined, error => {
...
});
```

index.d.ts

@@ -92,7 +92,7 @@ export interface CancelTokenSource {
 }
 
 export interface AxiosInterceptorManager<V> {
-  use(onFulfilled: (value: V) => V | Promise<V>, onRejected?: (error: any) => any): number;
+  use(onFulfilled?: (value: V) => V | Promise<V>, onRejected?: (error: any) => any): number;
   eject(id: number): void;
 }