[D1] Adding migrations_dir in Wrangler config chapter.

src/content/docs/workers/wrangler/configuration.mdx

@@ -400,6 +400,10 @@ To bind D1 databases to your Worker, assign an array of the below object to the
 
   - The ID of the database. The database ID is available when you first use `wrangler d1 create` or when you call `wrangler d1 list`, and uniquely identifies your database.
 
+- `migration_dir` <Type text="string" /> <MetaInfo text="optional" />
+
+  - The migration directory containing the migration files. By default, `wrangler d1 migrations create` creates a folder named `migrations`. You can use `migration_dir` to specify a different folder containing the migration files. For more information, refer to [D1 Wrangler `migration` commands](/workers/wrangler/commands/#migrations-create) and [D1 migration](/d1/reference/migrations/).
+
 :::note
 
 When using Wrangler in the default local development mode, files will be written to local storage instead of the preview or production database. Refer to [Local development and testing](/workers/testing/local-development/) for more details.