docs: add framework page (#12162)

* initial draft

* finalize page

* fix vale error

* changes to intro

* small fix

* added features list

www/apps/book/sidebar.mjs

@@ -128,6 +128,11 @@ export const sidebars = [
         type: "category",
         title: "Framework",
         children: [
+          {
+            type: "link",
+            path: "/learn/fundamentals/framework",
+            title: "Overview",
+          },
           {
             type: "link",
             path: "/learn/fundamentals/medusa-container",