feat: update README.md for ToC

Signed-off-by: Max Wu <jackymaxj@gmail.com>

Author: jackycute

README.md

@@ -9,6 +9,23 @@ CodiMD
 CodiMD lets you collaborate in real-time with markdown.
 Built on [HackMD](https://hackmd.io) source code, CodiMD lets you host and control your team's content with speed and ease.
 
+<!-- START doctoc generated TOC please keep comment here to allow auto update -->
+<!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
+# Table of Contents
+
+- [CodiMD](#codimd)
+  - [CodiMD - The Open Source HackMD](#codimd---the-open-source-hackmd)
+  - [Documentation](#documentation)
+    - [Deployment](#deployment)
+    - [Configuration](#configuration)
+    - [Upgrading and Migration](#upgrading-and-migration)
+    - [Developer](#developer)
+  - [Contribution and Discussion](#contribution-and-discussion)
+  - [Browser Support](#browser-support)
+  - [License](#license)
+
+<!-- END doctoc generated TOC please keep comment here to allow auto update -->
+
 ## CodiMD - The Open Source HackMD
 [HackMD](https://hackmd.io) helps developers write better documents and build active communities with open collaboration.
 HackMD is built with one promise - **You own and control all your content**: