Enable testing with vitest (#13)

Resolves #12.

Co-authored-by: Jos de Jong <wjosdejong@gmail.com>
Reviewed-on: #13
Co-authored-by: Glen Whitney <glen@studioinfinity.org>
Co-committed-by: Glen Whitney <glen@studioinfinity.org>

etc/vitest.config.ts

@@ -0,0 +1,16 @@
+import {dirname} from 'node:path'
+import {defineConfig} from 'vitest/config'
+
+const rootDir = dirname(__dirname)
+
+export default defineConfig({
+    test: {
+        includeSource: ['build/**/*.js'],
+        alias: [
+            {
+                find: /^@(.*)/,
+                replacement: rootDir + '/build$1.js'
+            },
+        ],
+    },
+})