doc: add an instruction to create a migrations directory (#3308)

* Update versioned-migrations.mdx

* Update versioned-migrations.mdx

doc/md/versioned-migrations.mdx

@@ -118,7 +118,7 @@ docker run --name migration --rm -p 5432:5432 -e POSTGRES_PASSWORD=pass -e POSTG
 </TabItem>
 </Tabs>
 
-2\. Create a `main.go` file under the `ent/migrate` package and customize the migration generation for your project.
+2\. Create a file named `main.go` and a directory named `migrations` under the `ent/migrate` package and customize the migration generation for your project.
 
 <Tabs
 defaultValue="atlas"