add introduction to all pages, move under table of contents

docs/src/docPages/api/schema.md

@@ -1,12 +1,14 @@
 # Schema
+
+## Table of Contents
+
+## Introduction
 Unlike many other editors, tiptap is based on a [schema](https://prosemirror.net/docs/guide/#schema) that defines how your content is structured. That enables you to define the kind of nodes that may occur in the document, its attributes and the way they can be nested.
 
 This schema is *very* strict. You can’t use any HTML element or attribute that is not defined in your schema.
 
 Let me give you one example: If you paste something like `This is <strong>important</strong>` into tiptap, don’t have any extension that handles `strong` tags registered, you’ll only see `This is important` – without the strong tags.
 
-## Table of Contents
-
 ## How a schema looks like
 
 The most simple schema for a typical *ProseMirror* editor is looking something like that: