Docs: Added an index files for profiles folder

This patch adds an index, for the design_documents/profiles
folder.Any new .rst file dropped there will be automatically
included.

Signed-off-by: Minos Galanakis <minos.galanakis@arm.com>
Change-Id: Ie4cd1b9bbd60ca462d4e77a4ed1bca467643dacc
diff --git a/docs/design_documents/profiles/index.rst b/docs/design_documents/profiles/index.rst
new file mode 100644
index 0000000..e856cf8
--- /dev/null
+++ b/docs/design_documents/profiles/index.rst
@@ -0,0 +1,12 @@
+TF-M Profiles
+=============
+
+.. toctree::
+    :maxdepth: 1
+    :glob:
+
+    *
+
+--------------
+
+*Copyright (c) 2020, Arm Limited. All rights reserved.*