fix: definition of NgxMapboxGLModule so it works with Angular 10

Co-authored-by: Dmytro Gokun <dmytro-gokun@users.noreply.github.com>

Author: BernhardRode

projects/ngx-mapbox-gl/src/lib/ngx-mapbox-gl.module.ts

@@ -81,7 +81,7 @@ import { VideoSourceComponent } from './source/video-source.component';
   ],
 })
 export class NgxMapboxGLModule {
-  static withConfig(config: { accessToken: string; geocoderAccessToken?: string }): ModuleWithProviders {
+  static withConfig(config: { accessToken: string; geocoderAccessToken?: string }): ModuleWithProviders<NgxMapboxGLModule> {
     return {
       ngModule: NgxMapboxGLModule,
       providers: [