docs(services): add new tasks in brand.service.ts

A couple of new tasks have been added into the `brand.service.ts` file.
The tasks aim to fetch models and stats of a certain brand.

Issue: #13
Signed-off-by: Mathis <yidhra@tuta.io>

src/services/brand.service.ts

@@ -126,6 +126,8 @@ async function getByIdBrand(brandId: string): Promise<IDbBrand | false> {
 
 //TODO get models of the brand
 
+//TODO get stats of the brand
+
 /**
  * Deletes a brand from the database.
  *