[HOTFIX] relative import in Auth.ts (#590)

Fixes this [build error](https://app.netlify.com/sites/kuzzle-admin-console/deploys/60099111179c6800077bab7a) (seen on the Amin Console Netlify build). Webpack looks for a package called `src/types/RequestPayload` since the path doesn't start with `.`.

Author: xbill82

package-lock.json

@@ -1,6 +1,6 @@
 {
   "name": "kuzzle-sdk",
-  "version": "7.5.1",
+  "version": "7.5.2",
   "description": "Official Javascript SDK for Kuzzle",
   "author": "The Kuzzle Team <[email protected]>",
   "repository": {

package.json

@@ -2,7 +2,7 @@ import { Jwt } from '../core/Jwt';
 import { BaseController } from './Base';
 import { User } from '../core/security/User';
 import { JSONObject, ApiKey } from '../types';
-import { RequestPayload } from 'src/types/RequestPayload';
+import { RequestPayload } from '../types/RequestPayload';
 
 /**
  * Auth controller
@@ -30,11 +30,11 @@ export class AuthController extends BaseController {
   /**
    *  Authentication token in use
    */
-  get authenticationToken (): any | null {
+  get authenticationToken(): any | null {
     return this._authenticationToken;
   }
 
-  set authenticationToken (encodedJwt: any) {
+  set authenticationToken(encodedJwt: any) {
     if (encodedJwt === undefined || encodedJwt === null) {
       this._authenticationToken = null;
     }
@@ -51,9 +51,9 @@ export class AuthController extends BaseController {
    * a developer simply wishes to verify their token
    */
   authenticateRequest (request: any) {
-    if ( !this.authenticationToken
+    if ( ! this.authenticationToken
       || (request.controller === 'auth'
-      && (request.action === 'checkToken' || request.action === 'login'))
+        && (request.action === 'checkToken' || request.action === 'login'))
     ) {
       return;
     }
@@ -383,7 +383,7 @@ export class AuthController extends BaseController {
   login (
     strategy: string,
     credentials: JSONObject,
-    expiresIn?: string|number
+    expiresIn?: string | number
   ): Promise<string> {
     const request = {
       strategy,
@@ -392,16 +392,16 @@ export class AuthController extends BaseController {
       action: 'login'
     };
 
-    return this.query(request, {queuable: false, verb: 'POST'})
+    return this.query(request, { queuable: false, verb: 'POST' })
       .then(response => {
         this._authenticationToken = new Jwt(response.result.jwt);
 
-        this.kuzzle.emit('loginAttempt', {success: true});
+        this.kuzzle.emit('loginAttempt', { success: true });
 
         return response.result.jwt;
       })
       .catch(err => {
-        this.kuzzle.emit('loginAttempt', {success: false, error: err.message});
+        this.kuzzle.emit('loginAttempt', { success: false, error: err.message });
         throw err;
       });
   }
@@ -507,7 +507,7 @@ export class AuthController extends BaseController {
    * @returns The refreshed token
    */
   refreshToken(
-    options: { queuable?: boolean, expiresIn?: number|string } = {}
+    options: { queuable?: boolean, expiresIn?: number | string } = {}
   ): Promise<{
     /**
      * Token unique ID