docs: update docusaurus to v3 (#5625)

* update dependencies

* update onboarding mdx

* fixes for mdx issues

* fixes for mdx compatibility

* resolve mdx errors

* fixes in reference

* fix check errors

* revert change in vale action

* fix node version in action

* fix summary in markdown

www/apps/docs/content/references/entities/classes/Address.mdx

@@ -49,7 +49,7 @@ An address is used across the Medusa backend within other schemas and object typ
   },
   {
     "name": "country",
-    "type": "``null`` \\| [`Country`](Country.mdx)",
+    "type": "``null`` \\| [Country](Country.mdx)",
     "description": "A country object.",
     "optional": false,
     "defaultValue": "",
@@ -76,7 +76,7 @@ An address is used across the Medusa backend within other schemas and object typ
   },
   {
     "name": "customer",
-    "type": "``null`` \\| [`Customer`](Customer.mdx)",
+    "type": "``null`` \\| [Customer](Customer.mdx)",
     "description": "Available if the relation `customer` is expanded.",
     "optional": false,
     "defaultValue": "",
@@ -130,7 +130,7 @@ An address is used across the Medusa backend within other schemas and object typ
   },
   {
     "name": "metadata",
-    "type": "Record<`string`, `unknown`\\>",
+    "type": "`Record<string, unknown>`",
     "description": "An optional key-value map with additional details",
     "optional": false,
     "defaultValue": "",