[gimp-web] Add a Table of Contents for 2.99.2 release news.

[Jehan <jehanp src gnome org>]

commit ead9df3c6255ee6e008ff5f213bd2f006fd290f5
Author: Jehan <jehan girinstud io>
Date:   Mon Oct 26 12:43:30 2020 +0100

    Add a Table of Contents for 2.99.2 release news.
    
    Syntax as provided by Patdavid. Thanks Pat!
    Because with several sections and subsections, it becomes a bit hard at
    some point which is under which section.

 content/news/2020/2020-06_GIMP-2.99.2_Released/index.md | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/content/news/2020/2020-06_GIMP-2.99.2_Released/index.md 
b/content/news/2020/2020-06_GIMP-2.99.2_Released/index.md
index a7e9577c..86cb4d8f 100644
--- a/content/news/2020/2020-06_GIMP-2.99.2_Released/index.md
+++ b/content/news/2020/2020-06_GIMP-2.99.2_Released/index.md
@@ -25,6 +25,8 @@ Release highlights:
 </figcaption>
 </figure>
 
+[TOC]
+
 ## GTK3 based UI
 
 The first difference will be visual as you will notice that GIMP got a