🔧 [#724] Add vite config file

An earlier prototype at least made `npm start` functional
with this config, and we'd like to have the build pipeline
(separate PR) use the same config as the tests.

vite.config.mts

@@ -0,0 +1,33 @@
+// https://vitejs.dev/config/
+import react from '@vitejs/plugin-react';
+import lodashTemplate from 'lodash/template';
+import {readFile} from 'node:fs/promises';
+import {defineConfig} from 'vite';
+import jsconfigPaths from 'vite-jsconfig-paths';
+
+export default defineConfig({
+  base: '/',
+  plugins: [
+    react(),
+    jsconfigPaths(),
+
+    // inspired on https://dev.to/koistya/using-ejs-with-vite-48id and
+    // https://github.com/difelice/ejs-loader/blob/master/index.js
+    {
+      name: 'compile-ejs',
+      async transform(_, id) {
+        const options = {
+          variable: 'ctx',
+          evaluate: /\{%([\s\S]+?)%\}/g,
+          interpolate: /\{\{([\s\S]+?)\}\}/g,
+          escape: /\{\{\{([\s\S]+?)\}\}\}/g,
+        };
+        if (id.endsWith('.ejs')) {
+          const src = await readFile(id, 'utf-8');
+          const code = lodashTemplate(src, options);
+          return `export default ${code}`;
+        }
+      },
+    },
+  ],
+});