fix warnings for any type

src/endpoints/account.ts

@@ -1,11 +1,12 @@
 import { BaseEndpoint } from './base';
+import { AccountDetails } from '../types/account';
 
 export class AccountEndpoint extends BaseEndpoint {
   constructor(accessToken: string) {
     super(accessToken);
   }
 
-  async details(): Promise<any> {
+  async details(): Promise<AccountDetails> {
     return await this.api.get('/account');
   }
 }