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/Entity/PlayerTexturesLoadingManager.ts

@@ -1,6 +1,5 @@
 import LoaderPlugin = Phaser.Loader.LoaderPlugin;
-import TextureManager = Phaser.Textures.TextureManager;
-import {CharacterTexture} from "../../Connexion/LocalUser";
+import type {CharacterTexture} from "../../Connexion/LocalUser";
 import {BodyResourceDescriptionInterface, LAYERS, PLAYER_RESOURCES} from "./PlayerTextures";
 
 

front/src/Phaser/Entity/RemotePlayer.ts

@@ -1,7 +1,7 @@
-import {GameScene} from "../Game/GameScene";
-import {PointInterface} from "../../Connexion/ConnexionModels";
+import type {GameScene} from "../Game/GameScene";
+import type {PointInterface} from "../../Connexion/ConnexionModels";
 import {Character} from "../Entity/Character";
-import {PlayerAnimationDirections} from "../Player/Animation";
+import type {PlayerAnimationDirections} from "../Player/Animation";
 
 /**
  * Class representing the sprite of a remote player (a player that plays on another computer)
@@ -22,7 +22,7 @@ export class RemotePlayer extends Character {
         companionTexturePromise?: Promise<string>
     ) {
         super(Scene, x, y, texturesPromise, name, direction, moving, 1);
-        
+
         //set data
         this.userId = userId;
 
@@ -35,9 +35,9 @@ export class RemotePlayer extends Character {
         this.playAnimation(position.direction as PlayerAnimationDirections, position.moving);
         this.setX(position.x);
         this.setY(position.y);
-        
+
         this.setDepth(position.y); //this is to make sure the perspective (player models closer the bottom of the screen will appear in front of models nearer the top of the screen).
-    
+
         if (this.companion) {
             this.companion.setTarget(position.x, position.y, position.direction as PlayerAnimationDirections);
         }

front/src/Phaser/Entity/SpeechBubble.ts

@@ -1,12 +1,12 @@
 import Scene = Phaser.Scene;
-import {Character} from "./Character";
+import type {Character} from "./Character";
 
 //todo: improve this WIP
 export class SpeechBubble {
     private bubble: Phaser.GameObjects.Graphics;
     private content: Phaser.GameObjects.Text;
 
-    
+
     constructor(scene: Scene, player: Character, text: string = "") {
 
         const bubbleHeight = 50;