switch to mocha for testing (#340)

.mocharc.json

@@ -0,0 +1,9 @@
+{
+  "exit": true,
+  "extension": ["ts", "tsx"],
+  "recursive": true,
+  "require": [
+    "./register-hooks.cjs"
+  ],
+  "timeout": 10000
+}

css-loader.mjs

@@ -0,0 +1,19 @@
+import fs from 'node:fs'
+
+export async function load(url, context, nextLoad) {
+  if (url.endsWith('.scss')) {
+    const content = fs.readFileSync(new URL(url), { encoding: 'utf-8' });
+    const classNamesMap = [...content.matchAll(/\.[\w\d]+ {/g)]
+      .map(([fromCss]) => fromCss.substring(1, fromCss.length - 2))
+      .reduce((prev, next) => ({
+        ...prev,
+        [next]: next
+      }), {})
+    return {
+      format: 'json',
+      shortCircuit: true,
+      source: JSON.stringify(classNamesMap)
+    }
+  }
+  return nextLoad(url);
+}