document the case of dependency class with private constructor

readme.md

@@ -58,6 +58,8 @@ const b = await manager.resolve('dependency-identifier'); //< `b` is of type `un
 const c = await manager.resolve<number>('dependency-identifier'); //< `c` is of type `number`
 ```
 
+Class with private constructor cannot be infered as class and thus need to be explicitly typed when resolved.
+
 ## Errors
 
 The `register` method throw an error if: