feat: add revalidate API route

Author: orinokai

demos/default/pages/api/revalidate.js

@@ -0,0 +1,8 @@
+export default async function handler(req, res) {
+  try {
+    await res.revalidate('/getStaticProps/with-revalidate/')
+    return res.json({ revalidated: true })
+  } catch (err) {
+    return res.status(500).send('Error revalidating')
+  }
+}