Enabling Outline back on actionable objects

Actionable objects (still a prototype) were outlined when you walk next to them.
The OutlinePipeline was broken when moving in Phaser 3.50+.

This PR completely removes the custom OutlinePipeline and replaces it with the rexOutlinePipelinePlugin
that is provided by a third party library and that works great \o/

front/src/rex-plugins.d.ts

@@ -1,4 +1,3 @@
-
 declare module 'phaser3-rex-plugins/plugins/virtualjoystick.js' {
     const content: any; // eslint-disable-line
     export default content;
@@ -11,6 +10,17 @@ declare module 'phaser3-rex-plugins/plugins/webfontloader-plugin.js' {
     const content: any; // eslint-disable-line
     export default content;
 }
+declare module 'phaser3-rex-plugins/plugins/outlinepipeline-plugin.js' {
+    import GameObject = Phaser.GameObjects.GameObject;
+
+    class OutlinePipelinePlugin {
+        add(gameObject: GameObject, config: object);
+
+        remove(gameObject: GameObject, name?: string);
+    }
+
+    export default OutlinePipelinePlugin;
+}
 declare module 'phaser3-rex-plugins/plugins/gestures.js' {
     export const Pinch: any; // eslint-disable-line
 }