Add bundlesize tests to UniversalLanguageSelector extension

To support us monitoring the amount of CSS and JS we ship to users
its imperative we start tracking the size of these modules statically
so we are aware when we increase the size of them.

Bug: T373017
Change-Id: I4c52d0216958a6595965e42f5416a24ee0c2054c

bundlesize.config.json

@@ -0,0 +1,10 @@
+[
+	{
+		"resourceModule": "ext.uls.interlanguage",
+		"maxSize": "0.4 kB"
+	},
+	{
+		"resourceModule": "ext.uls.interface",
+		"maxSize": "6.1 kB"
+	}
+]

tests/phpunit/structure/BundleSizeTest.php

@@ -0,0 +1,11 @@
+<?php
+
+namespace MediaWiki\Extensions\UniversalLanguageSelector\Tests\Structure;
+
+class BundleSizeTest extends \MediaWiki\Tests\Structure\BundleSizeTestBase {
+
+	/** @inheritDoc */
+	public function getBundleSizeConfig(): string {
+		return dirname( __DIR__, 3 ) . '/bundlesize.config.json';
+	}
+}