Complete carousel refactor.

Reduces one layer of DOM nesting for simplication, uses the latest Embla
version, unittests for everything.

vite.config.ts

@@ -0,0 +1,11 @@
+import { defineConfig } from 'vitest/config';
+
+// ts-prune-ignore-next
+export default defineConfig({
+  test: {
+    coverage: {
+      // Favor istanbul for coverage over v8 due to better accuracy.
+      provider: 'istanbul',
+    },
+  },
+});