Add initial plugin implementation and development setup

dev/app/my-route/route.ts

@@ -0,0 +1,12 @@
+import configPromise from '@payload-config'
+import { getPayload } from 'payload'
+
+export const GET = async (request: Request) => {
+  const payload = await getPayload({
+    config: configPromise,
+  })
+
+  return Response.json({
+    message: 'This is an example of a custom route.',
+  })
+}