Add-Ons Loader System (#606)

Implements an Add-on Loader so that other add-ons, such as the FFZ Add-on Pack, can be loaded directly by FFZ without requiring the user to install multiple extensions into their browser.

src/utilities/addon.js

@@ -0,0 +1,20 @@
+import Module from 'utilities/module';
+
+export class Addon extends Module {
+	constructor(...args) {
+		super(...args);
+
+		this.inject('i18n');
+		this.inject('settings');
+	}
+
+	static register(id, info) {
+		const ffz = FrankerFaceZ.get();
+		ffz.register(`addon.${id}`, this);
+
+		if ( info ) {
+			info.id = id;
+			ffz.addons.addAddon(info);
+		}
+	}
+}