with this change it's possible to pass a generic type `T` when calling `feature.getProperties<T>()` and using with TypeScript.

```
// before: const stop = feature?.getProperties() as Stop
const stop = feature?.getProperties<Stop>()
console.log(typeof stop) // "Stop"
```

closes openlayers#14868

with this change it's possible to infer the type `T` of passed properties when calling `feature.getProperties()` and using with TypeScript.

```ts
type Vehicle = {
  type: 'Car' | 'Bike' | 'Truck',
  color: string
}
const car: Vehicle = { type: 'Car', color: 'Red' }

// Before the change
const feature = new RenderFeature(car);
const properties = feature.getProperties();
// properties inferred as Object<string, *>

// After the change
const feature = new RenderFeature(car);
const properties = feature.getProperties();
// properties inferred as Vehicle
```

closes openlayers#14868