Merge pull request 'Redirect to OpenPlato' (#6) from learning-center into main

Reviewed-on: D-Net/openaire-graph-docs#6

docs/learning-center/_category_.json

@@ -1,8 +0,0 @@
-{
-  "label": "Learning center",
-  "position": 9,
-  "link": {
-    "type": "generated-index",
-    "description": "5 minutes to learn the most important Docusaurus concepts."
-  }
-}

docs/learning-center/open-plato.md

@@ -1,7 +0,0 @@
----
-sidebar_position: 1
----
-
-# OpenPlato Webinars
-<span className="todo">TODO</span>
-

docs/learning-center/tutorials.md

@@ -1,7 +0,0 @@
----
-sidebar_position: 2
----
-
-# Tutorials
-<span className="todo">TODO</span>
-

sidebars.js

@@ -98,13 +98,9 @@ const sidebars = {
       id: 'services'
     },
     {
-      type: 'category', 
+      type: "link",
       label: "Learning center",
-      link: { type: 'generated-index' },
+      href: "https://openplato.eu/"
-      items: [
-        { type: 'doc', id: 'learning-center/open-plato' },
-        { type: 'doc', id: 'learning-center/tutorials' },
-      ]
     },
     {
       type: 'doc',