add support to CUSTOM_ELEMENTS_SCHEMA inside playground/ui

[ntedgi]

in order to clear warning from logs at ui tests runs and ignore angular warnings for example

1. If 'p-fileUpload' is an Angular component, then verify that it is part of this module.
2. If 'p-fileUpload' is a Web Component then add 'CUSTOM_ELEMENTS_SCHEMA' to the '@NgModule.schemas' of this component to suppress this message.'

add support to CUSTOM_ELEMENTS_SCHEMA

at playground/ui/src/app.module.ts

change import { NgModule } from '@angular/core'; to import { NgModule , CUSTOM_ELEMENTS_SCHEMA} from '@angular/core';

and add schemas: [CUSTOM_ELEMENTS_SCHEMA] to @NgModule

the same as here

ref