test: create the vitest.config.ts file

This commit introduces the configuration of the
[Vitest](https://vitestjs.dev) which is the test runner used by the
whole application to load and validate Units, Components, and
Specifications.

Author: mrlemoos

vitest.config.ts

@@ -0,0 +1,24 @@
+/// <reference types="vitest" />
+/// <reference types="vitest/globals" />
+import react from '@vitejs/plugin-react'
+import tsconfigPaths from 'vite-tsconfig-paths'
+import { defineConfig } from 'vitest/config'
+
+export default defineConfig({
+  test: {
+    globals: true,
+    include: ['**/*.{test,spec}.?(c|m)ts?(x)'],
+    environment: 'jsdom',
+    setupFiles: ['./_/env/vitest-setup.ts'],
+  },
+  plugins: [react(), tsconfigPaths()],
+  ssr: {
+    target: 'node',
+  },
+  define: {
+    'import.meta.vitest': undefined,
+  },
+  css: {
+    postcss: require('./postcss.config.cjs'),
+  },
+})