docs: added plugins documentation (#10989)

(Should be merged after the next release)

Closes DX-1294

www/apps/resources/app/plugins/page.mdx

@@ -0,0 +1,21 @@
+import { ChildDocs } from "docs-ui"
+
+export const metadata = {
+  title: `Plugins`,
+}
+
+# {metadata.title}
+
+A plugin is a package of re-usable Medusa customizations, including [modules](!docs!/learn/fundamentals/modules), [workflows](!docs!/learn/fundamentals/workflows), [API routes](!docs!/learn/fundamentals/api-routes), and more.
+
+Plugins are useful if you want to re-use your customizations across Medusa applications, or you want to share those customizations with the community. You publish your plugin to NPM, then install it in a Medusa application to use its features.
+
+<Note>
+
+Learn more about plugins and their difference from modules in [this documentation](!docs!/learn/fundamentals/plugins).
+
+</Note>
+
+## Guides
+
+<ChildDocs showItems={["Guides"]} hideTitle />