feat: add plugin class

Author: gildas2k

src/plugins/plugin.js

@@ -0,0 +1,13 @@
+'use strict';
+
+export class Plugin {
+    constructor() {
+        this.usedByAComponent = true;
+        this.initialized = false;
+        this.callbacks = [];
+    }
+
+    onEvent(callback) {
+        this.callbacks.push(callback);
+    }
+}