Add TOC button to the markdown toolbar

www/common/common-ui-elements.js

@@ -997,6 +997,10 @@ define([
                     return '`' + str + '`';
                 },
                 icon: 'fa-code'
+            },
+            'toc': {
+                expr: '[TOC]',
+                icon: 'fa-newspaper-o'
             }
         };
         var onClick = function () {

www/common/translations/messages.json

@@ -599,6 +599,7 @@
     "mdToolbar_list": "Bullet list",
     "mdToolbar_check": "Task list",
     "mdToolbar_code": "Code",
+    "mdToolbar_toc": "Table of Contents",
     "home_product": "CryptPad is a private-by-design alternative to popular office tools and cloud services. All the content stored on CryptPad is encrypted before being sent, which means nobody can access your data unless you give them the keys (not even us).",
     "home_host": "This is an independent community instance of CryptPad. Its source code is available <a href=\"https://github.com/xwiki-labs/cryptpad\" target=\"_blank\" rel=\"noreferrer noopener\">on GitHub</a>.",
     "home_host_agpl": "CryptPad is distributed under the terms of the AGPL3 software license",