Docs: Enable Sphinx tabs extension

Enable the Sphinx tabs extension and fix the 'sphinx-trd-theme' typo.

Signed-off-by: Summer Qin <summer.qin@arm.com>
Change-Id: I18568465804f93e6cd2b71e344a673580cec993b
diff --git a/docs/conf.py.in b/docs/conf.py.in
index b4430c9..e2cd0be 100644
--- a/docs/conf.py.in
+++ b/docs/conf.py.in
@@ -1,6 +1,6 @@
 # -*- coding: utf-8 -*-
 #-------------------------------------------------------------------------------
-# Copyright (c) 2019-2020, Arm Limited. All rights reserved.
+# Copyright (c) 2019-2021, Arm Limited. All rights reserved.
 #
 # SPDX-License-Identifier: BSD-3-Clause
 #
@@ -50,7 +50,8 @@
     'm2r', #Support markdown files. Needed for external code.
     'sphinx.ext.autosectionlabel', #Make sphinx generate a label for each section
     'sphinxcontrib.plantuml', #Add support for PlantUML drawings
-    'sphinxcontrib.rsvgconverter' #Add support for SVG to PDF
+    'sphinxcontrib.rsvgconverter', #Add support for SVG to PDF
+    'sphinx_tabs.tabs' #Enable tab extension in Sphinx
 ]
 
 #Location of PlantUML