Migrate test runner from Mocha/Chai to Vitest

- Replace mocha/chai with vitest for simpler test configuration
- Remove jsdom window setup and jQuery initialization boilerplate
- Add vitest.config.mjs with jsdom environment configuration

Author: knowledgecode

test/test.mjs

@@ -1,10 +1,8 @@
-import { expect } from 'chai';
-import { JSDOM } from 'jsdom';
 import jquery from 'jquery';
 import param from 'jquery-param';
 
 describe('equivalence', function () {
-    var $ = jquery(new JSDOM().window),
+    var $ = jquery,
         test = function (obj) {
             expect(decodeURIComponent(param(obj))).to.equal(decodeURIComponent($.param(obj)));
         };

vitest.config.mjs

@@ -0,0 +1,9 @@
+import { defineConfig } from 'vitest/config';
+
+export default defineConfig({
+    test: {
+        environment: 'jsdom',
+        globals: true,
+        include: ['test/**/*.mjs'],
+    },
+});