Added API tests + added vitest.config.ts + added fallback of window.fetch with xmlhttprequest

vite.config.ts

@@ -1,18 +1,7 @@
-/// <reference types="vitest" />
-/// <reference types="vite/client" />
-
 import { defineConfig } from 'vite';
 import react from '@vitejs/plugin-react';
 
 // https://vitejs.dev/config/
 export default defineConfig({
-  plugins: [react()],
-  test: {
-    globals: true,
-    environment: 'jsdom',
-    setupFiles: './src/test/setup.ts',
-    // you might want to disable it, if you don't have tests that rely on CSS
-    // since parsing CSS is slow
-    css: false
-  }
+  plugins: [react()]
 });