Setting "importsNotUsedAsValues": "error"

Turning the "importsNotUsedAsValues" TS config value to "error".
This will require us to use `import type` instead of `import` when we are importing a value that is only used as a type (and therefore that is dropped by the Typescript compiler).

Why this change?
This is a requirement to be able to use Svelte in the future. See https://github.com/sveltejs/svelte-preprocess/issues/206#issuecomment-663193798

front/src/Phaser/Components/MobileJoystick.ts

@@ -1,5 +1,4 @@
 import VirtualJoystick from 'phaser3-rex-plugins/plugins/virtualjoystick.js';
-import ScaleManager = Phaser.Scale.ScaleManager;
 import {waScaleManager} from "../Services/WaScaleManager";
 
 //the assets were found here: https://hannemann.itch.io/virtual-joystick-pack-free