docs: fix transformer option in meilisearch documentation (#4250)

* Fixed documentation about meilisearch transformer function

* updated medusa-plugin-meilisearch readme

---------

Co-authored-by: Tsvetan Nikolov <tsvetan.nikolov@coliquio.de>
Co-authored-by: Shahed Nasser <shahednasser@gmail.com>

docs/content/plugins/search/meilisearch.md

@@ -141,7 +141,7 @@ const plugins = [
             ],
           },
           primaryKey: "id",
-          transform: (product) => ({ 
+          transformer: (product) => ({
             id: product.id, 
             // other attributes...
           }),